Dissolved Organic Compounds/DOC

Dear Prof.
Can excess DOC be linked to BGA in a planted aquarium and if that is the case,how can the DOC be removed?
Regards
Rudi

 

Hi Rudi,

Although there are many hypotheses about the causes of BGA, I have not heard that DOC can be linked to growth of BGA. However, the opinions about the causes of BGA are so diverse and so confusing that any opinion that I may express will cause even more confusion.

If you are concerned about DOC then filtration over activated charcoal will remove this, but then you must remove the activated charcoal after a few days as well. The easiest and cheapest way would be to do a water change which will remove anything else that may have built up in your aquarium as well.

Perhaps you can explain why you think that DOC is causing a problem in your aquarium?

Kind regards,

Dirk

 

I currently have a BGA problem and I'm working trough all the causes and cures I can find.
The plants suffered some CO2 defficiancy last month and that caused Red Brush Algea.I've got that sorted now but some of the affected plants leaves started to die
and I suspect leaching out nutriants.Then the BGA started.
I've red on PlantGeeks forum that excess DOC can cause BGA,so I thought by controling the DOC I can kill the BGA.

 

Rudi,

I think that you need to give us a detailed report of what has happened so that we can assess what your problems are.

Kind regards,

Dirk

 

Hi Prof Dirk,
A run down of my system:
3 foot ,100L
2/25w t8, 6800k each
silica sand substrate
internal cannister filter,600L/h spray bar
1/powerhead/flow pump
yeast based Co2, 2bottles,replaced alternatly every 4 days
ferts:flourish;2ml every second day
NPK ;10ml every other day
excel ;2ml every day
plants:heavily planted

vallisneria
java fern

anubia
Limnophila sp.-ambulia
cryptocoryne
Ludwiga Repens
fish:12 fish
Ph6
Nitrate 10mg/L
One of the Co2 bottles leaked and did not supply constant Co2.This has been rectified.
I do 50% water change every week.
10 hour light period.
There is no visible algae,only Green Spot Algae on anubia leaves and small amount of Red/brown brush algea on bogwood.
Hope this info is sufficient.
Regards
Rudi

 

Thanks Rudi,

This helps a lot to analyse your problem. One more question though: Where are you based? Why I ask this is because I want to get an idea of how hard or soft your tap water is.

Kind regards,

Dirk

 

I live in Kuils River.

 

Now that you have said where you live it explains all of your problems.

To begin with let me say which parts of your setup are in order:

Lighting, substrate and filter, but you should not have a spray bar as that immediately removes all of the CO2 that you have added.

In principle your fertilization is according to the prescribed schedule, but our tap water actually causes a major problem. All of these ferts are formulated for medium hard to hard water, in other words, water that contains enough Calcium, Magnesium and carbonate hardness. The Calcium and Magnesium is needed for plant growth but also to allow the iron chelate in the fertilizer to be delivered to the plants. The carbonate hardness is needed in order to allow your CO2 fertilization to work properly without major pH swings. Now, the problem that you have is that Cape water is so soft that it contains no Calcium, Magnesium and carbonate hardness and this means that all of the fertilization does not work. You have to fertilize very differently here to achieve decent plant growth, something that I have worked on for about 20 years now. I have formulated a plant fertilizer which overcomes these shortages. Currently, I am developing an additional fertilizer that works according to the EI method but I am not quite ready to release this as yet. However, you can obtain the basic ferts from me. This is the first step in improving your situation. I stay in Somerset West, so it is not too far away for you to collect some of these ferts from me. Send me your private email address by PM and I can send you a price list.

I hope that I can help here, but the Cape water is quite a challenge.

Kind regards,

Dirk

 

Thanks for the help Prof. Dirk.
I got some your ferts. from Gavin and Veronica last week,but I was using it on another,lower light,tank.
Will start with your ferts. on this particular tank tommorow.
Thanks again.
Regards
Rudi

 

Firstly, let us clarify that BGA is cyanobacteria. In fact, an organism we can thank for largely contributing to creating the ozone layer and allowing us to survive here on earth.

There are many opinions as to the cause of cyano, and I have done a bit of research. So just to help, I think I will list here what information I found so far.

Most likely the NO3 bottomed out (i.e. NO3=0ppm) for a day or 2 and now you have cyano. This often happens in tanks where people keep NO3 down to almost nothing with anaerobic filtration, but feed heavily and thus drive up the PO4. Have a look at the marine forums. Sure, the saltwater cyano is a different species, but still related. This also applies to some discus setups, in particular planted setups. This can also apply to heavily planted setups with a low fish load, where the plants end up using the NO3 so quickly that it just hits 0 for a while. A good example is a tank with a large carpet of glossostigma elatinoides and very high light. This plant is very NO3 hungry and under high light and with steady CO2 of 25ppm, can quickly remove all available NO3 from the water column.

The above can also be interpreted to mean an excess of PO4, but this would have to be a serious excess. Normally you would want your NO3 and PO4 to closely match the Redfield ratio, but when feeding, for example, beefheart and such foods heavily, then it is easy to see how one can get to the point of excess PO4. In experiments by Christian Rubilar from a Spanish fish forum (www.drpez.com) he also proved that he could add more PO4 than what is described in EI, as long as he increases the CO2 supply. He got no algae growth during this experiment. In this tank he had Anubias and was eventually running 9W/l of light! If you go look at some biology to see how these 2 work together, you will understand.

It is mostly argued that cyano is in almost all cases related to NO3 imbalance.

Other probable causes include low water flow, an ammonia spike, high DOC, and low O2. If you do some research, you will find most people say it originates in a low flow spot, such as on the substrate in a corner somewhere. This however, does not mean it stays there. Once it takes hold, it doesn't care about flow anymore.

There is also the argument that it can be caused by high DOC, which can be fixed by constant vacuuming and pruning of dead leaves and a few water changes. You can add charcaol, or Seachem Purigen, which is what I have used in the past. The latter is expensive initially, but can be regenerated and used for a long time over and over. It is a compound that acts by trapping particles of opposite electrical charge in a number of highly porous plastic beads. There are people who leave Purigen in their filters permanently, regenerate it and then return it. I would advise that you only use it when you need to lower your DOC if you suspect high DOC. That goes for all chemical media. Use as needed.

Low O2 is probably not a major cause, but can play a role. There are many accounts of people that had success in eradicating it by increasing flow and surface aggitation, which naturally resulted in O2 increase. At some point I read an article where the author made a comment regarding cyano's sensitivity to it's own metabolic waste, in this case, O2. This is rather true for most organisms - their own metabolic waste is fairly toxic to them. I have also found that as soon as I do not have enough surface movement due to blocked filter output/input/media or overgrown stem plants, then a thin white film develops on the surface and soon after that some algae growth starts in the tank. This is a good indicator for me and I use this to then do some trimming and cleaning. The film goes away as soon as I increase surface aggitation. And I don't mean create a waterfall effect like you get with HOB filters. Just some gentle movement to assist in gas exchange.

Blackouts are also highly effective. Cyano cannot survive without light. What you do is this:
1. 50% WC and test NO3 afterwards, ensuring it is at least 15ppm. If not, dose some KNO3 and you can find the calculations all over the web to dose the correct amount.
2. Switch off CO2, add a powerhead for flow and add an airstone to increase O2 through surface aggitation. If you have a spray bar you can also just drop the water level to achieve this effect.
3. Cover the tank. Must be pitch black. Absolutely no light entering the tank whatsoever.
4. Do not feed, do not open the covers.
5. Three days later open the covers. Do 50% WC and vacuum dead cyano and plant material. Feed the fish.

This gets rid of cyano, but does not guarantee killing it. Now you can address the original cause and hopefully it doesn't come back. And that is exactly where the problem lies. So many people have "killed" it, only for it to show up again a few weeks later...

You can also medicate the water. Prof Dirk sells a product which he says has worked for him in the past. This guarantees to kill all spores in the water. So does erythromycin (EM). The latter is an antibiotic which works on gram positive bacteria. Cyano is g-, but strangely very sensitive to EM.

At one point I thought I had cyano, but I couldn't identify it for sure. I am now of the opinion that is was not cyano, but just green filamentous algae that created a sheet between the fine leaves of Limnophila Sessiliflora and it resembled cyano. In an experiment in a seperate tank I could not kill it with an overdose of EM. I decided it was not cyano. Very often one gets a particular type of algae and then it is difficult to determine the exact cause. Even more dificult when you have more than one type together. So then you do everything you can.

In the end I propose a combination method:
1. Do a good cleanup - including the filter(s)
2. Blackout as described above
3. Correct fertilization strategy
4. Increase flow and O2
5. Increase CO2 if you are injecting CO2 and you have high light. Otherwise, dose liquid carbo daily without forgetting.

Now this has been a long post, but I hope this helps.
Regards
Lauré

 

Thanx Laure - that was a LOT of good info

 

+1 Thanks

 

Hi all

I want to resurrect this thread. It's a little old, but I've had some BGA problems recently. I've read over everything I wrote before and still agree. But what I would like to add is the following. I got BGA twice recently and both times after uprooting some plants and then doing really large water changes to solve the cloudy water issue. So 2 things come to mind. Organics from disturbing the substrate, and very low NO3 after the massive water changes. (2 x 75% WC's in one day). Comments?

 

Hi Laure,
Since I posted/asked this question,I've had some more experience with BGA and in both instances I was able to kill it with my own logic.
1) a imbalance between phosphates and nitrates.Either your phosphates are too high or your nitrates are too low.We cannot completely remove phosphates,otherwise the plants cannot absorb the nitrates.So I reduced phosphate dosing and increased nitrate dosing while keeping the rest the same.This worked for me.
2)If your phosphates are too low,no matter how much nitrate you dose,the plants cannot absorb it.Your plants will always have a nitrogen deficiency.
3)If the plants are healthy and show no deficiencies,the BGA stay away and other algae for that matter.

This is what I observed in my own tanks.In my most recent tank,the 40 l,for the first time,there is not even a single spec of any algae or BGA and all the plants is from a tank that was over run with BGA,BBA,hair algae,stag horn and just about everything in between.The only reason for this I can think off is that everything possible has been done to keep the plants healthy and growing optimally.

P.S. I still mix my own NPK fertz and these days, GH booster.

 

@Laure - my story is anecdotal but seems to concur what you are saying - seldom did a gravel vac on one of may well planted tanks - then beginning of the year decided that I need to put more effort into this specific low tech tank .. did a few gravel vacs and some rescaping a few times - now I see BBA has raised its ugly head. Never had algae in this tank before. So I wonder if too much care could also contribute to an imbalance - allowing algae to get a hold.

@Rudi - you still using trelmix ? Wonder if over / under dosing of trace okays a roll?

Later Ferdie

 

@f-fish,
General tank maintenance and hygiene are very important but doing a gravel vac is not a good idea.Pushing the vac. into the substrate and pulling it out again releases all sorts of nasties.
Yes,still using Trellmix.I'm definitely not overdosing traces.
Let me put it this way,how do you know you are overdosing or under dosing ferts.Because the bottle says you need to add a certain amount?What if the plants have "eaten" the prescribed amount of ferts in one day?
Now the plants "starve" for the rest of the week,or start to "eat" the nitrates provided by the filter.Result:nitrate = 0......= BGA
Nitrates must never fall to zero in a planted tank.