How much more can I add?

[finestic]

Adding more fish isn't just about space. It's about filtration too. What kind of filter are you running? If it's not strong enough, you'll have issues.

[kayzer]

Yeah, filtration's key. I've got a sponge filter and a HOB on my 20-gallon, and it handles the load fine. But if you're just running a basic filter, might wanna upgrade first.

[alixia]

Thanks for the advice, everyone. I'll hold off for now and maybe look into some plants instead.