I'm a "newbie" here, although I've kept tank-fish and other aquatics for over 50 years. I'm also a keeper and breeder of various Herps.
I have several enclosures for "mixed-communities"...eg: small hatchling temperate-climate turtles (non-agressive, non-fish-eaters), white clouds, rosie minnows, toads and newts. I'm wanting to explore adding several hardy algae-lovin' sucker-cats, if there are such things, that could tollerate the temp-fluctuations they'd encounter in these tanks...highs of up to 90*F (32.5*C?) and lows of down to 60*F (15.5*C?).
I'd hope these could compact (to about 6-8", 15-20cm?) at maturity. And I'd want them to be non-agressive, compatible community-mate, algae/water-plant-eaters. Everything in the tanks now gets along, so a turtle-hatchling/amphibian/fish-eating cat would not do!!!...

I live in the inland northwestern US, so would want to have them not be a species "banned" by wildlife departments there, if there are such species?
Anyone care to make any suggestions, given all these parameters?
(I'd also be open to suggestions for non-preditor scav-fish in an outdoor goldfish pond....greedy me!!!...

- Don,
keeper of (hopefully)
peacable kingdoms....