What temp are your tanks if kept at room temp? Axolotls are sensitive to higher temps. Ideally they shouldn't go above about 73F or so, and should have a strong air pump to keep aeration up if the temps rise a little.
I think one thing to consider is that axolotls come in a variety of colors. The breeder I got mine from has the following colorations: wild type, grey melanistic, black melanistic, white albino, gold albino, and multiple types of green fluorescent protein.
I would suggest more like a 40breeder or larger for axolotls unless you just want one by itself. Mine have been fine with fancy goldfish. They can both eat New Life Spectrum (my axolotls on NLS alone matched the growth rates the breeder I got them from achieved with his mix of worms, trout pellets, etc.). There is always a risk when you combine axolotls with anything, they are very easy targets for most fish to nip the gills off of them, or the axolotls will eat the fish.
They have to be on sand. Bare bottom can stress them out and wear out their toes since they have no grip, gravel can be swallowed and cause an impaction/obstruction.
Here is a shot showing a few of mine in with some goldfish.