Hi guys, I use drops to test PH. I tried about everything until i looked closer into the system and saw some yellow algae/mold growing. I just today took the complete system apart and gave it a good cleaning with bleach and then lots of good clean PH 7.0 water. It is now out in the sun drying off before i fill it and start over. I probably should of cleaned it this past winter, but I had lots of pepper plants growing. I flushed out everything down to the air hoses. I have a feeling that may had been my PH problem. Thanks for the help!!!