My Betta is currently in a 5 gallon tank. I bought a Fluval Edge 6 gallon for his new home. His tank has obviously cycled, but unfortunately the Fluval Edge has a different built in filter than the one that's in my current tank. Therefore, I don't think I can transfer the cartridge into the new filter for bacteria purposes. I'm also going with a different substrate in the new tank rather than gravel.

I was thinking of just using maybe half of his old tank water to fill up the new one and substitute the rest of the water with fresh dechlorinated water. However, I'm not sure if this is enough for the bacteria to transfer over. What do you think?

  • Using the water will usually greatly speed up the cycle, possibly even 10 - 20% of the normal 30'ish days. If there is any portion of your current filter you can put in the new tank, it will help a lot as well. – Jestep Jan 29 '16 at 21:11

No this won't cycle the new tank. The highest bacteria concentration is in the filter, substrate and decorations (plants, driftwood, etc.)

Betta are quite hardy fish so I would not really worry about it. But there are still a couple of things you can do to maximize bacteria transfer.

Squish as much things out of the old filter and drop it directly in the new one (use old tank water to rince the old filter). Transfer as much as possible of the old decorations in the new tank (particularly biological stuff) even if you plan to change them later. You can also use bacteria boost any fish store have to help cycle the tank faster.


Typically a new tank is seeded with gravel from an established tank, particularly if has an under-gravel circulator.

I don't know if a betta would appreciate or even like a big tank. They will normally find a secluded shelterd space.

  • Betta do like bigger tank, there are so many article about it. They do like to have more space to swim, more stuff to explore, etc. – Rémi Mar 4 '16 at 15:52

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