G'day,
While I believe the bio-wheel filter is one of the best innovations since the undergravel filter, it doesn't seem ideal for axolotls because as the name implies, the bio-wheel filter concentrates more on biological filtration and less on mechanical and chemical filtration. Here's the catch: Axolotls produce a lot of waste. If you don't have the appropriate mechanical filtrations to keep this in check the water quality will suffer. Sure you could diligently remove waste manually, however some debris is bound to evade your cleaning techniques. Bio-wheel filters do have small sponges, but these need to be changed regularly. Bio-wheel filters are particularly good at biological filtration because they bring the nitrifying bacteria in direct contact with atmospheric oxygen, whereas the bacteria in a canister filter rely solely on the limited oxygen in the tank.
zonbonzovi said:
I'm currently using a Marineland Penguin 100 for filtration, but w/o modification I am forced to hang it from the side of the tank.
There is no need for you to modify this filter. The bio-wheel filter works by virtue of the wet/dry filter, that is, it will actively use gravity to syphon water from the tank into its rotating wheel, which then contacts the nitrifying bacteria. Generally speaking, a bio-wheel filter is used primarily for smaller aquariums (i.e. no more than 55 gal). Also, the general flow rate for any given bio-wheel should be 5 or 6 times greater than the tank size. For example, a 55 gal tank would require 250-300 GPH. Clearly, you can see a problem with this already, as the flow rate might stress your axolotls. You're going to have to find a compromise.
zonbonzovi said:
In order for it to work properly, the tank has to be filled almost to capacity- not ideal for floating plants
Are you worried about your plants not thriving because the bio-wheel filter has the ability to diffuse the carbon dioxide concentration in your aquarium? If so, you only need to worry about this if the carbon dioxide concentration in your tank is artificially high for the benefits of plant keeping. This is the only instance where the bio-wheel filter will drive off the carbon dioxide level, but also bearing in mind any atmospheric air contacting the water will deplete the carbon bioxide to a significaly low concentration. In all honesty, plants aren't all that necessary when keeping axolotls but, of course, that's just my opinion.
Jay.