Filtration for ‘understocked’ tank…

[LittleDragon]

Hey all,
so I know the rule of thumb for axolotls is to have a filter rated for twice the size of the tank. My guy Fern is currently in a 20 gallon, but the hope is to move to a 40 gallon breeder at some point. Would a canister filter rated for up to 55 gallons be sufficient for a tank that size with a single axolotl? I do have an HOB rated for up to 40 gallons as well, but it would be nice to not need it.

Thanks in advance

 

[minorhero]

Hey all,
so I know the rule of thumb for axolotls is to have a filter rated for twice the size of the tank. My guy Fern is currently in a 20 gallon, but the hope is to move to a 40 gallon breeder at some point. Would a canister filter rated for up to 55 gallons be sufficient for a tank that size with a single axolotl? I do have an HOB rated for up to 40 gallons as well, but it would be nice to not need it.

Thanks in advance

The tank size ratings are a bit misleading. All canister filters rate the amount of water it turns over per hour. They also all lie about the numbers (because they measure the rate with the canister empty of media and with no head pressure. The rule of thumb is to take whatever the advertised numbers are and divide it in half to get the actual flow in your aquarium. You want ideally 4 to 8 times tank turnover per hour in actual numbers.

So for example. A Fluval 207 is rated at 206 gallons per hour. 206 / 2 = 103 gallons per hour actual flow. 103 / 20 = ~5 times turn over per hour. This is about as small a filter as you would want to use. If you find the flow too much you can always use a barbed ball valve on the return line to turn it down. But it probably won't be necessary once broken in. You could certainly buy a more powerful filter and tone it down if needed as well.

 

[JM29]

Hi,
I'm not very familiar of filter, but I understand that your filter is expected to treat the waste of 1 axolotl (convert its ammonia into nitrates).
Whether the axie is in a 20 gallons or a 40 should not be really important.

That said, minorhero's remark is particularly relevant.

 

[wolfen]

a canister filter for a 55 should be ok for a 40 provided the tank is cycled, it can be cycled at 2ppm provided only one axolotl is added.
if you are scooping the poop and cleaning food waste daily then the coarse and medium sponge can be removed and addition bio-media added which will allow it to be able to cope with a larger bio-load, most canisters have coarse, medium and fine sponge with a small amount of bio-media.
make sure the inlet has either a sponge or a guard over it to prevent accidents.