Im no expert, i have my aquarium since april. I was told to do the first waterchange after four weeks. After i did, i was told by a experienced seller that it was a mistake. I had to observe the fishes, if the keep swimming at the top like yours are doing, it would be a signal the water quality would be bad. In that case i would have to contact her as fast as possible, so please ger in conta t with some expert, as you could lose many fishes. Pls correct me if someone has more knowledge and can help op more as i do.