my tank has recently gotten these tiny little bubbles in it which makes the water seem murky. I have in the last two months added a few fish i now have 18 african rock cichlids in a 55 gal tank with two bio wheel filters and a heater. I did a 90 % water change and the water stayed clear for about a week. then slowly but surely the tiny bubbles reappeared. I have also tried different water clearing products. argh!!!! some one help please.