Hmmm, most people who keep planted tanks use sand in part of the substratum. I myself use playsand in my tanks(which is heavy and allows the addition of laterite and keeps the plant rooted better than gravel). I havent had any problem with fish eating sand or irritation of gills. In fact, many cichlids(one genus, Geophagus, are aptly named eartheaters) spend much of there time taking sand and passing it through the gills/mouth to get all the tidbits inside. Besides the fact that you cannot vacuum it the way you can gravel(you can't vac in a planted tank for the life of you anyhow) sand is perfectly acceptable for most aquariums. It is reccomended to use grains larger than 1 mm however.
Axos don't seem to pass water over the gills the way fish do, so even if the took in sand, it wouldn't go to the gills. If ingestion is a problem, then training them to eat from forceps should solve that quite quickly.
(Message edited by fishkeeper on August 20, 2004)
(Message edited by fishkeeper on August 20, 2004)