I am facing some problems in my freshwater aquarium and I would like your assistant.I purchased a 200 liter aquarium 2 weeks ago. My faquarium consists of 6 Mollie and 3 Labyrinth fish + 2 garbage cleaners. I am experiencing foam like substance on the surface of the aquaium.I emptied half of the tank and refilled it with clean water and cleaned all the filtes (external filter where water passes through activated carbon, ceramic then sponge material).I dis these procedure twice and still after cleaning in a couple of hours I get the foam-like substance on the surface. The temperature of the aquarium is 26 celcieus. I would appreciate your prompt response.Thank you.