My poor Betta has started acting strange and I only got him from the pet store a day ago. He has constant laboured breathing, his fins are all curled in and he swims around the tank in a erratic way. Most of the time he curls up against the thermometer and doesn’t move for hours. I have a 18 litres tank with a heater and filter. But I don’t have any testing kits, can anyone help me??!