Hey, I'm new so if I'm posting this in the wrong forum let me know and I'll move it.
I've got two bettas in separate 2.5 gallon tanks. They have the same heater, filter, pebbles and artificial plants. I set the tanks up at the same time. They've been living in the tanks for a few days. One of the tanks is fine, its staying clean and that boy (Dex) is happy, he's building a bubble nest in one corner. The other one is worrying me. The other fish (Lev) seems happy but hes not blowing bubbles, and there is a cloudy sweet smelling film developing on the top of the tank. What is causing this? Should I do a partial water change even tho the tank has only been there a couple of days? The tank holds pretty well at 79 degrees and I can see the filter spitting out water so I know it's working. The filter is the whisper 3i and the heater is a top fin 7.5 watt. I'm really worried my guy is gonna get sick