I just built the same size aero system out of same tub with 20 misters underside of tub 15 gallons of nutes and 12 inch bubbler on bottom. My plants are 2 weeks old and are on GH 3 part nutes they are in the system now for 4th day and looking healthy. My pH goes up slightly each day. more when I only had 10 gallons of nutes in ther. Now w/ 15 gallons seems to rise slower..3 points in one day..When should I add pH down what pH?...I added 2 gallons plain water in two days seems like thats whats needed 1 gallon day....I am useing RO water 7.0 pH...anyway ...Next week I will be getting a digital cam to show pictures.... Is it safe to post on this site? Can I wait two weeks to change nutes out? Low on money to buy more diamond nector? or can I mix only three part micro/grow/bloom...without diamond nector? only have 1 tsp per gallon of each part right now...Don't wanna burn plants again...Will be getting ppm meter in two weeks...Cant wait for the peice of mind....Big difference since I got the oakton pH meter three days ago!!!! HAPPY GROWING will be posting pics soon