what temp are you keeping the fish at? they are tropical fish, so you shouldn't let the temp get too low...78-82F is ideal for WAL and other african lungfishes. AUL's can tolerate lower temps--
--solomon
it's not necessarily bad, but it's not really necessary either. and if you are maintaining the fish in a temperate environment in the winter, then it's less work for your heaters to maintain water temp of 78-82 than it is for 85...you would also save some $$ on electricity...no point wasting energy if it's not necessary. in the summers i actually shut off the heaters on all my tanks...then again, most (except the SAL and AL's) can easily survive temperate conditions if necessary (gars, bowfin, AUL).--
--solomon