Changing Substrates

[Yubikiri]

Hello all! At the moment I've got a 55 gallon tank, and it is currently filled with gravel(and has been for years) and I would like to change that to sand, since my fish are getting bigger, and I don't want any of them(especially the knife fish) to swallow gravel by accident. My question is: if I change the substrate to sand, will the nitrogen cycle repeat again? I'll most likely leave a thin layer of the old gravel underneath the sand.

 

[Nils]

No, it won't restart the nitrogen cycle again because most of the beneficial bacteria live in the filter media. It will take a pretty big chunk out of the bacteria but you'll be fine IMO. Sand sounds good too, I think it looks so much more better than gravel. Also, just as a side note, that knife fish will outgrow your 55 if it's a black ghost knife. Need at least 150 gallons with the size they get.

 

[enrgizerbunny]

Don't leave any gravel, and I'd plan on a lot of vacuuming to get all the waste that is inevitably trapped in that gravel. I had to add water and then suck it out to carry poop after is removed all the gravel in mine. Your cycle will be fine, unless you use an under gravel filter (something tells me you don't).

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[ScotJudd]

I don't think you will have a problem with the cycle because, as stated above, most of the effective bacteria is held in the filter.
I have changed gravel and this is what I did.
For a couple of weeks at your normal water change do extensive gravel cleaning so that the majority of the waste is removed.
Then use a wide gauge tube to syphon the gravel out. Depending on the amount of water lost you might have to do this a few times over a few days rather than doing a huge water change in one go.
I wouldn't try to scoop the gravel out, you will end up with a very messy tank. Siphoning the gravel out is slower but almost totally clean so the fish won't be affected.
Hope that helps a bit.


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