I bought 2 danios and 2 rosey tetras for my 35l tank 3 days ago and then i read that they need more company so yesterday brought 2 more danios. They were swiming around since then very aggressively.
Today i saw one danio is staying like this, behind this rock at the back of the tank. Initially i thought he was stuck in there so i moved the rock a bit and allowed him to go. Then after few minutes he again came to this place.
Is this normal for them or should i be concerned. Also i saw one danio's tail fin is damaged.
Other fish seems ok.