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How to do a full substrate overhaul?

766 Views 4 Replies 5 Participants Last post by  tetra73
I'm thinking of doing a complete replacement of my existing substrate (as posted in my other thread, the Fluval Stratum is way too light and is frustrating to use).

Would doing a complete replacement disrupt the bacteria cycle of the tank???

I assume all that's required is to take the fish and existing plants out, and use the same water that's in there and remove old substrate and add the new.
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It's messy and a PITA, but it can be done. Accept that you won't get all of it out. I would recommend mounding as much of the old substate as you can to build your hills with if you are doing that sort of layout. Use a heavier substrate on top. Best of both worlds there. You will likely change most of the water since you will have a ton of crud floating around in the water column. It will disrupt the bacteria. You will have a mini cycle.
Roughly half the bacteria live in the filter. About 1/4 of it live in the uppermost layer of substrate. The rest live on all the surfaces all over the tank. In a heavily planted tank the plants are a major part of the bio filter, as long as they are growing well. Good light, CO2 and so on.

I would clean the filter a few days or more before, then not clean it for several days after, so as to keep these bacteria undisturbed.

There are a few ways to help out the bacteria colony, but are probably not needed if it is a densely planted tank and lightly stocked. However...

Get a bottle of bacteria that includes Nitrospira. Do not waste money on anything else.

Skim the upper layer of the substrate and put it in several mesh bags or nylon stockings. Hang these in an area with good water movement and remove them one a week.
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I personally wouldnt even clean the filter. Just drain the tank and scoop the crap out. Any remaining stuff can be flushed out by having a hose as an inlet then a drain hose that leads outside.

Then put all the new stuff back and turn the filter on. It will go into a mini cycle, but shouldnt be so bad. Maybe assist it by putting a mega dose of prime.

Its a pain in the ass, I have done it and I didnt even get the tank setup yet casue the tanks silicone was faulty.
This is what I would do. Get a 30g garbage can. Get enough for your tank water volume. Fill them up with water and let it age for couple of days with an air stone. You may want adjust the ph, gh, kh, and fert contents same as your tank water. Then, you turn off the filter. Remove all the plants and fish and put them in another tank or another bucket. Then, drain the tank water at the substrate level. Remove substrate. Drain out all remaining water. Put new substrate in and starting to rescape your new setup. Fill the tank with water from the plastic garbage can. Add fish. Turn back filter on. You may able to keep the filter running with water from the garbage can. When you are done, keep the lights off since your CO2 concentration is pretty low as this point with the new water and setup. Any additional light would promote algae growth. As long as your filter media has enough nitrification bacteria, you shouldn't need to cycle the tank again.
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