I'm new and have a 20l and a 70l tank fish-in cycling. I started with the 20l tank with 2 small platinum mollies one has spots and is a bit bigger. He is the one with odd behaviour. The filter system is above the water level so pours the water in creating bubbles and the molly liked to swim up against the flow and then back down and do it again ..... The smaller just swam around . As the bigger started bullying I set up the 70l tank and now have put him in there on his own. This tank is a Juwel and has the filter system in a box in the corner so no bubbles - now he spends a lot of his time swimming up and down the corner of the tank - the same corner all the time. I tried putting a backing on that side of the tank but made no difference. Is this just an odd fish or is it something that can be or needs to be remedied?