The tank is looking lovely. Very nice in my opinion.
In regards to measuring a tank and calculating the size in regards to stocking keep in mind that it matters how much water it holds. The footprint is not too big so I don't think there is any room for any more corys at least. Depending on how much gravel and decorations you put, the total amount of water will be signifficantly less than 90L. Same applies to the 30 litre. I have a 30 litre one which holds more than likely 20-24 litres of water. I normally measure my tanks the first time I put water using a bucket I know the size of.
Thank you! I fiddled around with it lots to get it how I like it. The black gravel and black background (I am assuming you are talking about the large tank here) really makes the plants and the fish stand out, and the cories love all their hiding places. Altlas loves the clump of floating plants and I am sure the new girls will as well.
Welp, that is interesting... So do you think the 90L will still be okay for the 6 cories I have now? I only got more in the first place because the peppered was all by himself. I wasn't planning on adding any more and there seems to be enough room for them. Once the glowlights are gone and I have moved Atlas it will only be them and the 6 female bettas in there.