I am currently keeping a smallish but adult bristlenose (c. 4 inches) in a 70 ltr Juwel tank. Not my own choice, but her mate turned out to be a bit of a sex fiend. The tank is otherwise lightly stocked, but I am finding I need to do twice-weekly water changes all the same, she is a bit messy. Ive also got extra filtration. In my case, that's fine, I've already got this fish and I want her to be happy, and preferably not to be overrun with fry every 3 weeks. But I don't think I'd have gone out of my way to buy her specially for this tank, if you see what I mean.