Cleaning a big tank

I have a 5ft tank (around 800L) with a 4ft sump filter. 3000L/h return pump. I have some clown knifes, plecostomus, Albino pangasius, rope fish and some other cichlids in there. Substrate is pool filter silica. This issue I have is that my tank's water is colored due to the cichlids bits some of the fish love. Not planted due to cichlids. I do regular water changes, but can only manage about a 100 L at a time due to the containers I own. The substrate is getting dirty as well and has never been cleaned in around 2 years that the tank is running.

I was thinking of doing a huge 90% plus water change (or even full tank replacement) by siphoning existing tank water into a 4ft tank and temporarily hosting the fish there, whilst draining tank, clearing substrate and refilling with fresh H2O. Filter medium in sump is good and I think the water should cycle fairly quickly. An existing canister would be used on new 4ft tank to keep the fish happy.

Any thoughts on problems that I might experience and how long the cycling might take before moving fish back in, taking in consideration that filter media will not be changed at this stage.

 

I would NEVER do a complete change.

Rather do an 80% water change with a very good gravel vacuum.

You loose too much with cleaning the gravel. Remember the bacteria don't only colonize your filter, but also colonize your substrate. Now here's a huge difference of opinion, but I've read that it can take only a few weeks to establish the bacteria on the filter, but up to 6-8 months to establish in the substrate.

 

Agree with Zoom here.

 

Why not multiple smaller water changes like 20% every 3 days, u cud do one on the weekend and one on wednesday and then the weekend again, large water changes will cause nitrite spikes especially if you are going to be stirring up that dirty substrate, u can always add PSB or similar to help replenish the bacteria loses.

 

5 foot=800L?

 

hi zoom, i think you are correct, apparently, based on various articles on the net, the bacteria colonies "seat" and establish themselves in the lower or deeper levels of the substrate, this is one of the reasons why its important to try not to disturb substrate too much when vacuuming, besides releasing potential trapped nitrite and ammonia of course as well.

the benefits of using seeded substrate from mature cycled tanks in new tanks have been proven by the experiences of many of us here, and i've read that a handfull of mature gravel can clear a bacterial bloom (new tank syndrom) over night!

its clearly a serious part of a keeping a healthy tank..

---------- Post added at 13:09 ---------- Previous post was at 12:09 ----------

must be a VERY DEEP and WIDE tank or the combined volume of tank and sump?

 

Correct. Tank is ex marine custom tank of 70 high x 65 wide by 150 length = approx 650 L at water height + approx 150 L in the 4ft sump.

Noted the "DO NOT DO 100%" sentiment, but the substrate is fine silica sand, and through the glass I can see dark brown "dirt: at the bottom (some places up to 4 cm), this is partly why I wanted the full tank cleanup. I can normally not vacuum the substrate as the tank is way too deep for the commercial vacuum pipes, so i think I am overdue on the substrate clean. So I take it that I have to go down only halfway down the substrate and NOT clean it totally?

 

i think, the dark brown "dirt" that you are seeing, may in fact be the deep "embedded" bacteria and not dirt. i've heard that it does dis-colour the substrate once its seeded. because generally, dirt doesnt filter down through the fine type substrates, being so tightly packed together, its gets swept up into your filter much easier that way...

personally, i think if your fish are happy and healthy, i wouldnt fix something that isnt broken, your little eco-system might just be doing great and you may end up disturbing that delicate balance, especially if your ammonia, nitrites, etc readings are consistently good.. so i would say, as they guys above suggested, do 20% water changes every few days or even every day for a week, disturbing that gravel as little as possible( i.e. do not go into the gravel at all only skim the surface lightly), and i think that would sort out your dis-colouration problem.

let us know which route you choose to go with and how it turns out

 

I would still advice AGAINST this. However, let us know whichever route you take, and the long term effects.

 

Will do. thank you for the advise.

 

I don`t know about that, even fine gravel will trap dirt in some way. Gravel in an older tank can look super clean but if you stir it up it will be filthy.

 

this may also just be wastes that have already been broken down by good bacteria, and not harmful to the fish..

but we'll have to wait and see the end results, at least we will learn something from his experience..

 

please sent a pic of your tank?

 

Decided to remove most water from tank, but leave sump intact. Cleaned the gravel, not removed and cleaned "properly", but stirred it by hand to remove most visible trapped dirt or whatever it was. tank was refilled with aged water and sump was restarted. It did color the water a bit. It was left for a day and a half. Water was tested and nothing out of the norm. Fish was put back in. I added ac to the sump. Tank is almost clear now. Will be doing another 10% wc today. Will post pics soon.

 

cool dude, i would just monitor ammonia / nitrates for the next week or so to be safe..

 

I wonder how they clean this tank? :bigsmile:
Monster Tank installed at the Radison Hotel in New Jersey...

 

Scuba gear?

 

I (as big as I am) can swim in there!!!