I setup my 20 gallon tank specifically for red claw crabs which I'm getting when the nitrogen cycle is done (don't worry, I know what I'm doing for the cycle 
) so I have the tank just over half full as I have a dry land area. I picked up a fluval U1, with the gravel and decor there's around 13 gallons in the tank. It's just a single stage sponge filter...after looking at other setups online I get the feeling it may be inadequate for my setup and that it doesn't have the capacity to contain enough beneficial bacteria. I bought it because it's meant for low water levels and it's a compact size and decent build quality. Do you guys think this filter will keep my tank clean and free of toxins? I'll have 1, maybe 2 crabs and possibly 2 fish in the future.
Also in the manual it says to replace the sponge every 3 to 6 months...but wouldn't I lose all my benefical bacteria?
) so I have the tank just over half full as I have a dry land area. I picked up a fluval U1, with the gravel and decor there's around 13 gallons in the tank. It's just a single stage sponge filter...after looking at other setups online I get the feeling it may be inadequate for my setup and that it doesn't have the capacity to contain enough beneficial bacteria. I bought it because it's meant for low water levels and it's a compact size and decent build quality. Do you guys think this filter will keep my tank clean and free of toxins? I'll have 1, maybe 2 crabs and possibly 2 fish in the future. Also in the manual it says to replace the sponge every 3 to 6 months...but wouldn't I lose all my benefical bacteria?
