My 15 gal is currently stocked with a pair of honey gourami and 8 Galaxy Rasbora. Could I fit in a group of 4/6 pygmy Cory's? The tank is planted and I have a Superfish eccoflow canister filter 120 that pumps 400l/h.
I think you'd be ok with that but go for the 6 rather than 4 Assuming you have neutral water and a sand substrate - the Galxies do better in harder water and the cories better in softer but both species are quite hardy so would do well in neutral.