So you have like a 52 gallon reservoir.. That seems to be a pretty weak solution mix up for your GH 3 part.. Not very aggressive imo.. I use this for my 40 gallon res.
Here is the nutrient regimen I use and how I control PH with little or no ph up or down...
So OK - feeding schedule week by week. This is the GH weekly feeding program, slightly tweaked. I will only call out the volume of each part per gallon of water in the following manner: grow, micro, bloom, ppm range. Example - 5-2.5-2.5-400/800 would mean 5 ml grow, 2.5 ml micro, 2.5 ml bloom and a ppm of 400-880. Remember it's per gallon. You Euro's can easily convert to liters. 4 liters is just a little bit over 1 gallon. It should also be noted that I use the hardwater micro due to my tapwater. I suggest using the hardwater micro in place of the regular micro if your tap water is over 200 ppm total or you have over 70 ppm Ca. RO water users should use the regular micro.
Veg -
week 1 5-2.5-2.5-400/600
week 2 10-5-3- 600/800
week 3 12-6-3 800/1000 (continue week 3 formula if additional veg time is required.)
Bloom
week 1 6-6-10- 800/1200
week 2 3-7-12 - 1000/1400
week 3 3-8-14 - 1000/1400
week 4 3-8-16 - 1000/1400
week 5 (discussed in detail below*)
week 6 0-7-20 - 1000/1400
week 7 0-6-20 (see bleow**)
* During week 5 if not using a booster like Superbud,
Bushmaster Kabloom etc. run 2.5-7-18. I use
MOAB (Mother of All Blooms) or
BushMaster at 50% of recommended strength, and use 1.25-3.5-9 for the fert base.
**If running an 8 week strain you should only run the ferts during week 7 for a maximum of 3-4 days. This gives you 10 days for flushing.
The ppms work out almost exactly. I tend to lean toward the lower side of the range, unless I have a really heavy feeder that I know can handle it.
At every ressy change out I add in 5 drops per gallon of 35% food grade H2O2. During flush use ph adjusted water at 5.5-6.0
I will add epsom salt at week 1 of bloom if the plants are heavy feeders AND I see signs of an Mg def. Otherwise I won't use it. The only time I have ever had Mg def is during transition. The GH 3 part is a little low on Mg, but the PBP and Canna nutes are way lower.
Now- how to control your PH...
There are a couple factors that cause your PH to drift. The most common is running the nute solution too strong or too weak. If it's too strong, your PH drops. If it's too weak the PH rises. You have to find the balance point. If you find that the formula above is say, a little strong, and say you have a 20 gallon ressy, mix the nutes for 18 gallons. If it's a little weak, mix it for 22 gallons. You follow?
The other common mistake is mixing your nutrient solution and trying to adjust the PH right away. You have to allow time for the ph buffers in the nutrient solution to do their job. Mix the nutes up, and bubble or circulate for 12 hours before even looking at your PH. You will find the PH to be almost right on target.
I use little or no ph adjusters. (Except during flush). I use tap water, with a starting PPM of 300-400 and a starting PH of 7.4-9.0 (Thats crazy you say! The water is too hard, you will never get stable PH and you will have too much Ca, causing a lockout of Mg!) Bollocks I say.
Every week, on Friday I drain the ressy and fill with plain water. I let that run overnight giving the plants a little flush. This also allows the chlorine and ammonia to evap. On Saturday morning, I mix the nutes into the ressy. I DO NOT adjust ph at this time. Let that run as is overnight. On Sunday morning, I check ph and adjust if needed. Usually don't have to.
Doing things this way has saved me from constant PH drifts, and using about 150 ml of ph down every ressy change, and a little here and there throughout the week to keep it in the desired range. Now, the most I ever have to use is about 30 ml.if any at all. (I have a 35 gallon ressy btw) My Ph stays at a constant 5.5-5.8.
