I was sad to lose the tetra too, but glad to solve the problem before we have guppy fry in there. We've added a very tiny albino bristlenose pleco today, so we'll see how it adjusts.
I put a bigger filter in too - the one I had to swap in was only for 20 gallons, so I put a new 30 gallon one in and moved the other back to the 20... along with the new heater (which may end up being run in tandem with the other, since I see they're the same model... so underpowered.) The 20 gallon wasn't getting up to temp despite the heater being supposedly for 10-30 gallons, so...
Thanks for stopping by. (I've seen 5 of the shrimp today, so it's a good day!)