fishtank decorations

Hey! I’ve woken up this morning to one my female bettas dorsal fins/ tail fins torn. I did a 50% water change 16th and let sit till today 18th to check parameters see below Nitrate=20 Nitrite=0 Ph=7.0 Kh=80 Gh=120 Ammonia= Couldn’t measure (out of test strips and didn’t realise) I’ve had...

i have recently bought a fake rock for my tank and when i used sand it was weighted down quite well but i found that the sand was getting dirty too quickly and i was disturbing the fish too much so we went and got some gravel however when i put the rock in it now keeps floating as it is hollow...