A softshell turtle in a ank with fish will eventually eat them the day you are late or one early morning while the fish are cor nered thier will be no fish. Turtles like softshells eat fish hands down it is only a matter of time before he gets fast enough or big (assuming he is still young since the fish are living with him more then 5 days) enough to eat them. The only way for fish to live with any ominvorous, or carnivorous turtles(ie. softshell, sliders ) is in a huge water volume minimum 400 gal. so the fish can have plenty of space to manavuer & see the turtle coming. Even then it depends on the size of the fish & turtles involved more or less space may be required. I've seen an 8 in. softshell shred 12 in red devils 14 redtail cats in 250 gal tanks. Bigger fish just makes easier to catch he is not ignoring the fish he is just waiting for a time for them to be caught off guard & he'll eat them.
Glad you have a pr. a well as the loiselli; but why risk losing the fish? The only turtles I've ever been able to keep fish with more then 3 months. were small slow movers likes mud/musk turtles & babies of other species & the fish were much bigger also.
