I think its a good question of the ST's would die off. Maybe nothing to eat. But tanks don't have to have iso's. Although there's nothing wrong with it either, obviously. I keep a good ST population because I my two different species, one being Chazuta's like to eat them, and they do a good job of eating and dead FF's that may be there. I saw a group of them once feasting on one. Hopefully they also eat frog doo too!