So I have a 30 gallon planted tank. I have 3 cories, 3 kuhli loach, 1 platy, 2 dwarf frogs, and 3 painted tetras. Can I still add more fish in there? If so. What kind of fish?
As said above, the cories should have a school of at LEAST 6 of the same species, not a hodge podge mix. The kuhli's will also appreciate at least 3-6 more of their kind. As for the painted tetras, up their school with at least 3 of the same species, but try to get the natural coloration to stop promoting the dyeing process.
As for the ADF, they do thrive in a species only environment as they find it very difficulty to find food in a tank with fish as the fish can rely on scent and sight to find food, whereas the frogs primarily use their sense of smell as they see in only shadows and are nearly blind.
A nice little 5 gallon system would be perfect for the pair of ADF.
So, a recommended stocking for the 30 gallon is:
6+ Cories of the same species, 6-10+ kuhlis, 6+ tetras and the platy. What gender is your platy? If male then you could toss in a few more males for more color and mid area movement. If female then leave it as solo for a few months to make sure it does not have any fry (females can store sperm for a few months, you want to make sure she is empty / virgin. If she is then you can get a few more females but only buy them if they are in a female only tank or if you have the space to quarantine them for a few months. Otherwise the fry will over stock your tank within one birthing.
The tetras will shoal nicely once their group has been increased.
Please note, ALL new fish have to be quarantined for 30 days to keep your current stock healthy.