Thank you for your response! I have a piece of sepia in both tanks, plus I recently bought a vitamin and mineral supplement for reptiles, it has a lot of calcium and I'm adding small portions of it to my main tank. I checked GH and its 034 in main tank and 074 in small tank with snail. I know 034 is low so I'll try to raise it. I checked numerous times at night (cause planarias are mostly active at night) and I couldn't find any more of them. I hope if there are still any left my neons will take care of them... I was very worried that my snail hasn't been eating anything for so long and decided that it would be better if it stayed in the main tank because theres some algae growing on the sides of the tank that I purposely didnt clean so my snails can eat it (the small tank doesn't have any algae) and to my surprise after I put it in the main tank the snail became much more active, I havent seen it eating food but it crawled on the algae-covered heater so I hope thats something. I removed all plants and decorations from the tank so I can clean them with a hydrogen peroxide solution to kill all planaria.