Get rid of the belly heat and plan to purchase larger enclosures in the VERY near future... D m rubidus don't do well with belly heat, a radiant heat panel, placed high in the enclosure, would work best, but they are best maintained at room temperature with access to low 80's for a couple of hours per day, though they should always have a cool retreat available... Feed them as varied a diet as possible, smaller more frequent meals work best, and while fish will create a stench and mess of legendary proportions, its a great part of a varied diet... Just be certain to use fish that are thiaminase free, such as crappie, trout and blue gill.