Hi there. Just getting back into fish after a few years out, and have a question. My tank has been cycled for a few weeks, and I have the following fish in it: 5 rosy zebra danios, 6 dwarf neon rainbows and 2 small corys. I would like to add 2 or 3 more corys, as I know they like to be in small schools, but I'm thinking I may be maxxed out already. It is a planted tank, and the plants are doing very well. My filter is a whisper 20i, and I'm wishing I had gone bigger. I do roughly 30% water changes every 2 weeks. Can I safely add the extra corys, or would they be too much for the tank? TIA.

Going by the usual 1 inch of fish per gallon, you're maxed.
Going by your post - you want someone to say it's ok.
The truth? The cory probably won't die if you put them in there but you already know it's not ideal. If you're going to do it, you're also going to make sure that the water parameters are acceptable so I'd say it's not going to be the worst kind of overcrowding I've heard about.
cb

Corys like to be in a school of at least 5. You can easily add three more Corys. Make sure you have good filtation and some aeriation to bring up some of the bootom water in your high tank. My experience with Neon Rainbows is that they are a somewhat decate fish. They do fine in my 55G but not in my 20.

Words of wisdom from clep.berry there. All I'd add is if you do it, the 30 percent every 2 weeks should be weekly.

I agree, I think if you up'd your pwc's to once a week you'd have a better chance at it, also id definetly look into upgrading your filter

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10g- 3 variatus, 4 guppies, 1 blue mystery snail
40g Breeder- 6 danios, 5 swordtails, 1 Opaline Gourami
"I was born with nothin and I still got most of it left."- Seasick Steve.

If you do I'd at least wait a month or two for your tank to be better established because it sounds like your tank hasn't been set up long and is already fully stocked. I prefer to keep tanks lightly stocked but just how much you can get away with is partly based on things like water changes and your filter, live plants can help too.

6 dwarf neons are too much for a 20 gallon. They are just dwarf compared to the rest of the rainbows still a decent sized aquarium fish, i have one in my 90 gallon that is pushing 3".

Thanks, everyone. I will up my water changes and likely add another filter.