But he said he use peroxide and it can be bad for beneficial bacteries... cilica raise the ph as calmag, but nutrient base(food) use to low ph... so when mixing the nutrients , you must start (if use them) with cilica and calmag, they will raise the ph considerably, sometime more than 8.0, after it, the nutrients base will decrease that ph, after you run the pump, the plants get some nutrients and the mediun itself filter some nutrients as a result you will experience a ph raise if the ph was high in the water before you ad the nutrients... I run my pump all the time 12 hours non stop while the lights are on, at the begining it hapen in this way or when plants are small, 1st or 2 nd week cause the plants barely eat, but after it when I fill my reservoir, next day, the ppm raise and the ph decrease, the ppm raise because the water evaporation or the temperature of the room, and ph decrease because the water is more acid for the descomposition of nutrients and bacteries that growing in it, i just ad plain water that will low the ppm and raise the ph and put more volume in my tank to compensate the level... I dont add nutrients or ph up to my reservoir until next week when I put the new food, I use clay as mediun, so before I run with a new food I let the system run just with water a full day to clean salts and stuff stick on the clay, pipes, feeders, and tank, and I use that day of water to add the peroxid or any incepticide or antifungal if I going to use them, also sm-90 raise the ph too. I try to be away of the ph busters, trying to find a balance between hard water, water from the deshumidifier or AC that are ppm low but ph 7.0, and the nutrients that low ph, and cilica and calmag that raise the ph.. if you play with those factors, the need of ph busters will be reduced... but every nutrients brands or kind are diferent, so you have to find out how to mix the ones you are using, to change amounts to get a more perfect balance for you final food... I have a 45 gallon tank that I mix with nutrients to 35 gallons, and it is ok, i get the perfect number in that way, if I prepare my mix based in 45 gallon, my final mix will be to high and I will need to pur water on it so it will be more than 45 gallons... but I put the nutrients for 35 gallons in a 45 gallons of water, so I have 10 gallons to play with if the ph is low I can add cilica or calmag for thoses 10 gallons without pass over the amount recomended for the manufacturer... also if the ph go to low I be able to add less base nutrients that low the ph... I will try everything before I decide to use any ph buster that have no beneficial ingredient for a plant...