Lecture 3 - Sumps and How they work

[Zafgak]

Lecture 3 - Sumps and How they work

There seems to be a lot of dis or maybe mis information about Sumps.

That they are for professionals only
That they always flood your house in a power cut
That they are finicky ancd hard to keep going
etc. etc.

Neither of the above are true, they are in fact relativley easy to set up and use, provide good filtration and are easy to clean. So what is a sump ????

To be continued .................................................. ......

[warren]

Couple of things to consider.

Canisters are very quiet. There are very efficient at chemical, biological, and mechanical filtration. However, they are more time consuming and difficult to clean.

Sump type filters can be noisy, especially for tanks that weren't built with drilled bulkheads. Using an overflow box can be funky and if it is not designed well you can empty several litres of water on your floor. However, most sumps can be "cleaned" ...simply remove the mechanical media and rinse out the debris. Unfortunately, due to these filters being easy to neglect people often don't clean out the mechanical filter media and debris ends up in the bio-media. These filters can efficiently breakdown most forms of organic nitrogen and the result is they become nitrate factories. This can be largely avoided by being diligent with cleaning the mechanical media on a routine basis.

[Madam]

Hi Warren,
Saw your post comparing canister filters and sumps, and it seems like you have some insight.
I know a guy who can set up a sump for me in a way that it is fairly quiet, and will not overflow in power outages. When you talk about cleaning "mechanical" stuff, are you talking about the actual filtration media? (Ie, rocks, white fluff, etc)
I currently have a small canister filter in my 60L tank, and I find it quite easy to clean out when I need to. So you're saying that sumps are even easier than that?
Do you have any thoughts on box filters? (built-in filters - don't see them very often)

[neilh]

Getting it not to overflow in power outages is not that big a deal. I think Warren is referring to filter floss, the white fluffy stuff and other bio-mechanical media designed to trap detritus.

Sumps aren't always that easy to clean. They are generally much much larger than any canister filter, which means a lot more filter media and a fair amount of glass making up the sump.

I had to clean out my Discus sump the other day, 900LX450WX400H, and it was definitely not easier than a canister filter. Draining it, moving media into buckets with water and physically moving it out of the cabinet was hard work.

Nothing wrong with box filters, just that you lose tank space to them. eg your tall 4ft is now a tall 3ft in terms of swimming space

[butcherman]

Sumps aren't always that easy to clean. They are generally much much larger than any canister filter, which means a lot more filter media and a fair amount of glass making up the sump.

I had to clean out my Discus sump the other day, 900LX450WX400H, and it was definitely not easier than a canister filter. Draining it, moving media into buckets with water and physically moving it out of the cabinet was hard work.



it takes me 10 min a week to maintain my tank with sump its easy. How often do you clean or maintain your sump neilh?

[neilh]

Every water change. A complete sump clean out is a totally different story :p

[brads]

hey this is a old thread I found when searching for explanations on how fw sumps work. I wanted to find out how they are built , how much noise they make and any other common problems and there solutions .
basically the tips of the trade from people who have them .

would be cool if this lecture was started ?
this could form a great reference for all members

in the meantime ill continue searching the net just I trust your guys views more

cheers

[Zoom]

Brads,
I'm hoping that someone will come on and share how a sump works... unfortunately I know old fart (i.e Zafgak) is extremely busy at the moment. He is hardly ever online these days. Maybe Vee can take over?

[butcherman]

A sump it there to take out all of the equipment and filter media out of the main display tank.
Your water gravity feeds into the sump where you can make it flow through differnt filter media as you please. The water can also be heated and is then pumped back into the main tank.
An added bonus is the increased water volume you get on your tank.
As for the noise well it all depends how you gravity feed the water and how you design your overflow system. personally my overflow was as quiete as a mouse.

[guido.coza]

Hi all
Don't know if this belongs in here. I have a 4 chamber(filterfloss>gravel>sand clearwater) filter BEHIND my tank. No noise no possibility of running dry or flooding the floor. Does this also qualify as a sump??

[butcherman]

i think (with out having seen your tank) by the sounds of it you have more of an intank filter but i think it would hide everything quite nicely

[snyper564]

This is my diy behind the tank sump it works in reverse to the below the tank sump the water enters the sump from a powerhead inside the tank and when the water in the sump is above the tanks water level it runs back into the tank after passing through the 4 chambers. My tank is spotless thanks to the 1st filterwool chamber the pipes u see running into the bottles are airlines because i have many power failures and they keep all the benf bacteria alive here are some pictures and plans.


Here is my new DIY biofilter.
This design is closer to a true sump and can hold a lot more bio media than the 1st one I built and is also a lot more convenient as the lid can be opened and closed as needed which was quite a task with the 1st one.
The containers are cut off 2l bottles, therefore the sump is cheap and affordable a plus when your a student.
This is basically how it works
The power head provides mechanical filtration as the water is pushed towards:
-1st compartment – filter wool mechanical and bio filtration
-2nd compartment – plastic pot scrubbers bio filtration
-3rd compartment – bio balls bio filtration
-4th compartment – ceramic rings bio filtration
The filter fits neatly on a shelf behind the tank. And is nicely hidden from the front view. There is only one trick to this filter keep the return water pipes water level above the tanks water line and you will have no problems just make sure the outlets are at least double the width of the inlets. This filter/sump provides an additional 6.25l Bio filter to my 72l tank the possibilities are truly endless for the behind the tank sump. If you have space behind the tank you can use 4 x 10l cylinders and modify accordingly. The overflows are safeguards in case something blocks the flow pipes and there are airlines run into the filter to run whilst there is a power cut on battery power to ensure all the bio bacteria have enough oxygen and don’t all die off. You can add another 4 compartments and add chemical filtration a heater and more bio filtration. The corner filter you see is only there to provide bio filtration to the tank in power cuts as we have many in my area and aeration is not enough when its 12+ hours. The water is still crystal clear there is minimal movement within the tank as the tank is planted and needs minimal movement the tanks water is very stable as the 2 otos I have, have had no problems and all the fish are happy and healthy. I just have lace curtain to cover the sump to make sure nothing falls in. It works on the same principle as the 1st one and wen there is a power cut the water drains only 1-2cm allowing all the media to stay wet and then the battery pump supplies the oxygen through water movement to them and the main tank. Here are the plans and the pictures hope they help. - from my diy post ( http://www.tropicalaquarium.co.za/showthread.php?t=3642 )

[butcherman]

wow thats some serioius macgyver stuff snyper... but it would get the job done and easy to maintain

[snyper564]

wow thats some serioius macgyver stuff snyper... but it would get the job done and easy to maintain

And its super cheap and affordable :bigsmile:
you can do the same with 5l containers etc and really bump the total capicity

[guido.coza]

Hi Snyper
What happens if for what ever reason something blocks the return pipe to the tank. If you put the pump INTO the filter the worst that happens is the pump can run dry. Just a thought but i might be wrong!

[snyper564]

Hi Snyper
What happens if for what ever reason something blocks the return pipe to the tank. If you put the pump INTO the filter the worst that happens is the pump can run dry. Just a thought but i might be wrong!

Every chamber contains an overflow you can see this in the plans for this exact problem everything was taken into account before the plan was put into action to prevent any possible problems. With regards to the 4th and final chamber that leads into the tank - this chamber is filled with ceramic rings and a 3cm gap is left between the outlet and the actual ceramic ring level as ceramic rings naturally sink there is no way that the outlet pipe can ever get blocked. Hope this answers your question. This could have been a prob if the 4th chamber was filter wool or something that floats

[guido.coza]

I had ones a eel going thru a outflow untill eventually he got stuck for what ever reason i never found out. I didn't wonna critisise your system just share my experience.

[snyper564]

I had ones a eel going thru a outflow untill eventually he got stuck for what ever reason i never found out. I didn't wonna critisise your system just share my experience.

No worries. Its through experience being shared that experience is gained u can only better ur designs and ideas if u listen to everyone who had had prior experience. Thanks for the info. I don't keep eels in my system but to prevent this u can cover up the intake pipe to the filter in my case I have a powerhead with a sponge trap that will prevent this. Glad u mentioned it though as many powerheads don't have this precaution and have to be covered by something like stockings etc

[Stormer]

Gravel cleaner for Oscar tank:
Since we are on the topic of sumps i was wondering if this would work.
http://www.tropicalaquarium.co.za/picture.php?albumid=146&pictureid=826
It begins on the left side:The water flows over the gravel from the one side and enters the left side,it then goes up a pipe (which is about as hight as the water level to act as an overflow) and down into the sump,it then goes thru the filter media to the other side where the water pump pumps it back up into the tank where the cycle repeats itself.

(only for big tanks with big fish that like to be messy) :D

[snyper564]

Gravel cleaner for Oscar tank:
Since we are on the topic of sumps i was wondering if this would work.
http://www.tropicalaquarium.co.za/picture.php?albumid=146&pictureid=826
It begins on the left side:The water flows over the gravel from the one side and enters the left side,it then goes up a pipe (which is about as hight as the water level to act as an overflow) and down into the sump,it then goes thru the filter media to the other side where the water pump pumps it back up into the tank where the cycle repeats itself.

(only for big tanks with big fish that like to be messy) :D

Its a good idea and i think it might work. You will just have to enure that the pipe is above water level to prevent a siphon effect from happening the main problem i see is running 3 powerheads in perfect harmony what i mean by this is that 3 have to fill the sump and at the same time push the water up at the same speed if there is a blockage in any one of these powerheads you can have big problems.
1. PH to the sump blockage - PH in sump can empty the chamber entirely.
2. PH to the tank blockage - Sump will overflow
3. PH receiving from the sump blockage - sump will overflow.
This is why sumps use overflows from the main tank. as opposed to PH

Another problem is the holes you will have to drill in the acutally glass for the powerheads, as this is a tank for oscars that glass will be very thick and if anything goes wrong you will have to replace either a side or the entire tank.

Stormer its a very good idea, the trick to what you want to attempt is simplicity remember that gravity is your friend. This is a very big project but with alot of planning and ensuring that everything is functioning correctly you can set it up - and you will have a very low maintenance tank then too :)

[Henk Hugo]

its actually a very bad design - NEVER have a pipe under the water level more than what you want to sump to drain during a power failure.

[SalmonAfrica]

I think what Henk is trying to say is that if you have a pipe at that level in the water, in the event of a power failure, your tank will siphon up until that point....

[Henk Hugo]

exactly - a breather hole can get blocked and then you have a flood of note

[snyper564]

Thats what i said :) good idea just put more thought into the design. Its a massive undertaking and should not be attempted until everything is perfect. So stormer bring future plans here so we can discuss any problems we may see. Rather change a design than flood the house

[riyadh]

As far as i am concerned. sumps and cannisters are practically the same thing. Main differences being volume. On average a sump will filter 2 to 3 times more than what a cannister can. However if you have the right setup with cannister filter and another filter, be it an internal bio filter or OHF then you should be fairly close to what a sump can do for your tank. Personally I dont like a sump from the maintenance aspect. It takes alot longer to clean than cannisters. I can move my whole cannister and clean it in the yard but a sump would have to be emptied first. Todays technology has brought us cannister that now filter 2000 to 3000L per hour, this should bring on very close to what a sump can filter. Just my opinion based on my experience.

[butcherman]

i assume you have a course gravel?i agree with henk the water will syphon out you need to rather skim the surface water

[butcherman]

Gravel cleaner for Oscar tank:
Since we are on the topic of sumps i was wondering if this would work.
http://www.tropicalaquarium.co.za/picture.php?albumid=146&pictureid=826
It begins on the left side:The water flows over the gravel from the one side and enters the left side,it then goes up a pipe (which is about as hight as the water level to act as an overflow) and down into the sump,it then goes thru the filter media to the other side where the water pump pumps it back up into the tank where the cycle repeats itself.

(only for big tanks with big fish that like to be messy) :D

If you really want to use this kind of system you would need to create an overflow system with a syphon break that would start automatically when the power comes back on. here is an idea that might work, but you would need to reasch a little more In the picture below, The red pipe stops sucking water when the water level drops. and starts again what the water level rises. the green pipe would direct water from the bottom of the tank to the surface. personally i would just skim the water from the surface and vacuum the substrate a little more, much less complicated.:bigsmile:

[neilh]

On average a sump will filter 2 to 3 times more than what a cannister can.
Where did you pull these figures from? Thumbsuck?

Average capacity of a canister filter is what 15l? Average sump size is say a tall 3ft ie 90X30X45 which is ~120l. Thats a fair amount more space for filter media when compared to a canister.


Todays technology has brought us cannister that now filter 2000 to 3000L per hour

Don't confuse pump return rates with filtration capability. Just because a canister can return at 2000 to 3000 litres per hour, doesn't mean it will effectively filter 2000 to 3000 litres

[butcherman]

Where did you pull these figures from? Thumbsuck?

Average capacity of a canister filter is what 15l? Average sump size is say a tall 3ft ie 90X30X45 which is ~120l. Thats a fair amount more space for filter media when compared to a canister.



Don't confuse pump return rates with filtration capability. Just because a canister can return at 2000 to 3000 litres per hour, doesn't mean it will effectively filter 2000 to 3000 litres
Agreed
its far better to increase your system total volume that to increase your systems turn around time.
more volume means a more stable environment for your fishies.

[snyper564]

If you really want to use this kind of system you would need to create an overflow system with a syphon break that would start automatically when the power comes back on. here is an idea that might work, but you would need to reasch a little more In the picture below, The red pipe stops sucking water when the water level drops. and starts again what the water level rises. the green pipe would direct water from the bottom of the tank to the surface. personally i would just skim the water from the surface and vacuum the substrate a little more, much less complicated.:bigsmile:

Thats the perfect solution to the problem.
Now only have a PH in the sump this will give enough force to move the water to the tank and to move the poop towards the siphon now all you have to do is fine tune 1 ph instead of 3.


Agreed
its far better to increase your system total volume that to increase your systems turn around time.
more volume means a more stable environment for your fishies.

This is true as adding a sump effectively adds the sump litres to your entire system.
Examples
70l tank + 8l sump = 78l tank
120l tank + 30l sump = 150l tank
300l tank + 120l sump = 420l tank.

This is how you can easily bulk up your system litres and increase as butcherman said the tanks stability.

[riyadh]

Yerah agreed, hence why i did sya main difference being volume, obviously i should have said main difference being the volume that a sump can filter, sorry I wasnt clear enough to you or anyone else


Where did you pull these figures from? Thumbsuck?

Average capacity of a canister filter is what 15l? Average sump size is say a tall 3ft ie 90X30X45 which is ~120l. Thats a fair amount more space for filter media when compared to a canister.



Don't confuse pump return rates with filtration capability. Just because a canister can return at 2000 to 3000 litres per hour, doesn't mean it will effectively filter 2000 to 3000 litres

[Stormer]

Thanks guys,I appreciate the help.

[Kuhli Loach]

Stormer – I like your idea, but like some of the other members said, it will have to be fine tuned to prevent all the water in the tank from draining into the sump, and then causing the sump to overflow. I think it is possible to have the sump return pipe at gravel level, connected to a spray bar, but you will have to install a non-return valve. In the even of a power or pump failure, the non-return valve will prevent a siphon being formed. The outlet from the tank to the sump does not have to be at the gravel level, but can be at the water level of your tank. Most of the detritus will be suspended in the water column due to the current flowing over the gravel, and will find its way to the outlet. The outlet will have to be designed in such a way, that it does not get blocked, causing your tank to overflow from the volume of water in the sump being pumped into the tank. I would use nothing less than a 50mm diameter pipe for the outlet to the sump. The 50mm diameter pipe can take more flow that a 25mm, giving you the option of using a pump with a higher liters per hour rating.

[Zafgak]

A sump is nothing more than an extra water container usually underneath an aquarium where you can place equipment, provide different types of filtration ( mechanical and biological), add top-up water to the tank and perform other maintenance tasks

There is no - one best design of sump - Generally they are designed to suit the owner. Bigger is better, as the sump is a way to add water volume to the tank without the tank taking up more space in your room. It is also a place to put your heaters, pumps etc. which means a better looking tank.

The picture shows a general sump design - water is taken from the main tank, piped into the sump. The water flows in on the "dirty side of the sump, is then forced to flow under the baffle into the next chamber. The water then flows over the next baffle into the "clean" side of the sump, where it is pumped back up to the main tank.

In general, where the water enters the sump, filter wool is placed in this compartment, which is a mechanical filter to take out solids etc. The filter wool also provides a breeding ground for bacteria. The second compartment traditionally has bio-balls as a substrate for bacteria breeding. The final compartment, which should now be clean water, is where top-up water is added, heaters are positioned, Aeration and medicines can be added and is then pumped back to the main tank.
The second picture is a photo of what a sump generally looks like.

In effect the sump is just a larger version of a HOB or Canister filter.

More compartments can be added to do specific functions if required. You could add a compartment in which you grow out plants, which also reuces nitrates at the same time. The combinations are only limited by your imagination.

What are the benefits of having a sump


It makes an ideal place to put heater(s), and other equipment, because you don't have to figure out ways to hide all this stuff when hung on the outside or placed inside an aquarium, and it saves on space.
It is an ideal place to put bio-media for biological filtration, as well as perform additional mechanical and chemical filtration.
It is the perfect place for dosing meds and ferts also topping up tank water.
It adds beneficial tank water volume to your system.
It can provide additional aeration to your system.
It can contribute to improved quality of the aquarium water.
When set up properly, it can act as a back up water overflow system if the power fails.


What are the drawbacks of having a sump


Unless you do your water volume calculations correctly it can be a flood hazard in power failures. Do your calcs correctly and this is not a problem.
If your tank is not drilled an overflow box can be a bit tricky to start and stop after power failures. But there are ways to overcome this.
It can siphon back through the pump during power failures. Again watch your inlet placement and put a one way valve on the inlet pipe from the pump.


Conclusions


A well designed and thought out sump is a better filter than most, and provides larger water volume which is always a good thing. It is easy to clean and maintain.

[butcherman]

just a question zafgak?
wouldnt a heater in the return chamber(ie last shamber) be dangerous?
it the water level in the return drops to low ie failed overflow or due to evaporation. the heater could potentially burn out or explode

[Zafgak]

just a question zafgak?
wouldnt a heater in the return chamber(ie last shamber) be dangerous?
it the water level in the return drops to low ie failed overflow or due to evaporation. the heater could potentially burn out or explode


Good question - I have never had this problem occur, the evaporation is normally taken care of by top-ups.. I have never seen a failed overflow, but it would cause a problem. One way around that is to have the heater below the intake level of the pump...

[butcherman]

I have seen heaters pop cause they have been in the last chamber. Would another way around this be to have the heater in the first chamber? it would never run dry.

[keith1964]

Lecture 3 - Sumps and How they work

There seems to be a lot of dis or maybe mis information about Sumps.

That they are for professionals only
That they always flood your house in a power cut
That they are finicky ancd hard to keep going
etc. etc.

Neither of the above are true, they are in fact relativley easy to set up and use, provide good filtration and are easy to clean. So what is a sump ????

To be continued .................................................. ......

I would be interested with this information as I am new to having a sump tank set-up.

[veegal]

Keith the lecture continues in this thread. See post number 34.

[Gert Combrink]

I have seen heaters pop cause they have been in the last chamber. Would another way around this be to have the heater in the first chamber? it would never run dry.
OR the second, it all depends if there is a opening under the first baffle!
- If the water goes through the first chamber, under the first baffle, and over the second baffle!
All depends how the sump(baffles) are configured.
There's the correct answer! :idea:

[sarf]

I'm running a sump on my 2m tank..since i'v done this,i dont think i'l consider getting another large tank unless it has a sump..the benefits far outweigh the disadvantages..also..with regard to problem of water back siphoning into the sump and flooding the room..there is a simple solution..i'v made a hole in my return pipe where the water gets pumped back into the tank..put the whole jst below where the water level would be when the pump is on..that way,if power cuts..the water level drops,and the siphon is stopped coz air gets in thru the hole..problem solved

[Apoc]

Hello all,

Got a bit of a sump question ( which may seem silly – my apologies in advance ! :p ) so I thought I might as well post it here….. I need to replace the baffles in my sump and was wondering what the BEST configuration for the first baffle / chamber is ? Gert eluded to two options and I’d like to know what would be best…

IE: Should the first baffle be placed high to allow water from the over-flow to flow underneath into the second chamber, OR should the first baffle be place from the bottom up to create a settlement chamber wherein water from the overflow collects in the first chamber and then flows OVER the first baffle into the second ?

What would the most Co2 efficient option be ( as tank will be planted ), and would the second option ( settlement chamber / water flows OVER first baffle ) not also create a bit of a safety net should a fish end up in the sump somehow ? :wondering:

[butcherman]

No question is a stupid one. firtly there is no optimal configuration, there is only what works best for you.

What equipment do you want in your sump and what filter material do you want to run?

[Apoc]

Well its quite a small sump ( only 100L or so ) which came with the tank, and I cant upgrade just yet... so using what I got, there will only be about two compartments for media so I will probably go with normal mechanical filtration in the first ( Filter wool / sponge or similar ) and the second chamber will probably be bioballs for Bio filtration... would also like a heater placed in the sump ( now the question is where should this go ? ), and obviously the return pump in the last chamber ?

[butcherman]

Sounds like you got a good idea of what you want. For safety put the heater in the first chamber. Never put the heater in the return chamber if the chamber runs dry your heater will pop

[roderickc]

Hi Guys

Thinking of Building a sump for my tanks with a trickle filter (as the Prof Suggested). I have been looking for the perfect way to run the overflow with not much success. I am going to build one this weekend and let you know how it comes along. one question thought is if the power cuts off and the power comes back on do will the overflow start automatically?

I have seen the overflow in drilled tanks but mine will not be drilled.

[Apoc]

Will do, thanks Butcherman ! So do you think the first baffle should be placed from bottom up to allow water to flow OVER the first baffle then ?

[neilh]

First chamber for detritus settlement ie over rather than under, otherwise it will end up in other chambers all over your filter media. Learnt this the hard way

[Ferryman]

I had to 'edit' my sump to add more chambers, but currently it goes under over under and over into an empty spill-over chamber. To stop the detritus issue, I have a nylon mat in first chamber and inflow runns water through it first, every week i take out the mat and hose out all the solid gunk (leaves, snails etc)

[Apoc]

Great, thanks for the replies guys - Will go with the first baffle being from the bottom up to allow water to flow OVER into the second chamber.... I prefer that idea, was just wanting some input / confirmation first...

[butcherman]

I had mine like this the filer wool stoped the detritus from getting to the rest of the sump.

[TroyFish]

I need some help with a sump.

1st time ever doing a tank with one.
Mine looks like this
http://i755.photobucket.com/albums/xx194/troyfish101/AS.jpg

What should go where? Is this right?

[butcherman]

A basic setup from right to left.

1st chamber overflow and heater.

2nd chamber filter media

3rd chamber return pump

[TroyFish]

Thanks bud. Sounds simple enough!

[Singularity]

Is this going to be a planted tank ?

[TroyFish]

Is this going to be a planted tank ?

Is this question for me?

I am still thinking about it, but more than likely will go that way

Have read that it isnt a good idea as it removes the Co2?
But have also read that it makes no difference.

[Ferryman]

I found some threads on MonsterFish's site where the guys discussed this issue, if the overflow drop isn't harsh, and the sump can in some way be sealed off, less gassing off would occur, but all in all, sumps do apparently cause gassing off more CO2 than canisters contribute

[TroyFish]

I found some threads on MonsterFish's site where the guys discussed this issue, if the overflow drop isn't harsh, and the sump can in some way be sealed off, less gassing off would occur, but all in all, sumps do apparently cause gassing off more CO2 than canisters contribute

Water only needs to drop...70cm:p Once up and running i will monitor everything.

[Whipme]

What I've been seeing more and more on foreign forums is a filter sock under your overflow pipe. Like the one seen on a pool gobbler. Apparently it helps capture bubbles and a lot of dirt, like a pre-filter.

Basically what you'd do is have it suspended right under your overflow pipe, hanging down from a plastic sheet with a big hole in it for example.

[Singularity]

What I've been seeing more and more on foreign forums is a filter sock under your overflow pipe. Like the one seen on a pool gobbler. Apparently it helps capture bubbles and a lot of dirt, like a pre-filter.

Basically what you'd do is have it suspended right under your overflow pipe, hanging down from a plastic sheet with a big hole in it for example.
They have been in use in SA for a couple of years, cost about R400 for bracket and sock
http://i278.photobucket.com/albums/kk85/singularity96/26082010116.jpg

[Whipme]

That's pretty cool, but way over-priced and not the same material as the one I'm thinking of. It's actually a thinner material, most likely a nylon or polyester mesh.

I'm sure you could easily make something like that for under R100 given the right materials :)
How does that one work for you?

[butcherman]

That's pretty cool, but way over-priced and not the same material as the one I'm thinking of. It's actually a thinner material, most likely a nylon or polyester mesh.

I'm sure you could easily make something like that for under R100 given the right materials :)
How does that one work for you?

if your looking for a cheaper solution make a plastic ring and place a regular sock in it. works like a dream ;)

[CharlieB]

I found a great and easy solution to the siphon problem if there is a power failure is to simply add a partition in your over flow box that is hanging off the outside of your tank . Make the partition the height that you want your water level to be( but obviously not higher then the overflow box walls :p ) Now have your drain hole at the bottom of the one compartment and then have your siphon tube in the other compartment. This way you have basically created an overflow with in your overflow box and if the power fails your siphon tube will stop siphoning as soon as the tank level drops below the water level in your overflow box compartment. Whats also great about it is all you need in your tank is your siphon tube and nothing else so hardly takes any space. Tried and tested and works like a charm :) Very hard to explain but I hope this makes sense.

[CharlieB]

Another advantage about a sump which no one has mentioned I think is that it keeps the water level in your tank constant and instead its your sump that looses water through evaporation and or in my case also from your cat drinking out of it! I love not waling into a room to find my tank suddenly looking low and water :)