Idontknowwhattoputhere

So basically my 20 gal long tank I believe has planaria worms.. This is worrying to me I'm not exactly sure what to do. Its my first tank and we've have hair algae growing on my moss, a bunch ramshorn snails, and now planaria. I noticed this today. I knew before that we had detritus worms but these clearly look different from them detritus worms. They are on the glass and the have a more pointed/triangular head. I don't know were the came from as we havent added anything new to the tank and just doing our regular cleanings (cleaning the glass every week, removing hair algae, and gravel vacuuming every other week). It may have come from the plants that the ramshorn snails came on. Any tips?? I don't want my fish to be hurt but I dont have any other tanks set up that I could move them to. Nor do I have the space for another 20 gallon tank. At most I have space for a 5 gallon which isn't enough for 6 lemon tetras (one is a baby).. Any products y'all recommend? Any tips or items you recommend is very much appreciated. Happy holidays

Update: Power is back and fish are doing good 👍 Temperature is back to normal and everything is running normally

My power went out this morning and I have a heated fish tank. We keep the tank at 78°F and the temperature has gone down to 77-76°F. Will it harm my fish if the power stays out for longer? I dont have anything in my tank that's battery powered everything is plugged into the wall sockets (airstone, filter, heater, and my light.)

I've seen them chase eachother a few time but never actually hurt eachother. Nor have any of them tried to hurt/nip at the mystery snail. His shell is closed tight. I've never seen his body hanging out of his shell or anything like that. I might put an algae wafer in the tank to try and see if he'd come out of his shell for that.

Ive had a mystery snail in my tank for about 2 months. For about 2/3 weeks I havent seen him move. I feed him alage wafers 3 times a week but ive stopped since I noticed he was just in his shell. He might be moving at night cause most mornings his shell is moved in some different position. I tried smelling his shell cause I heard that their shells would smell if they were dead. But it just smelt like nothing. I havent found a clear answer on whether or not mystery snails hibernate. The tank is heated and has lemon tetras in it. I'm not sure if its something to do with ph level in the tank because we added crushed coral to it cause originally the ph was acidic (6.3) and it was raised to 7 which is neutral. I'm not sure whats happening with him. Is it something to do with winter or that warm water makes mystery snails more active? Please help!!