Anyone familiar with aluminum sulphate?

im in 5 gal buckets, ph is sitting high at about 7 - 7.5. tried flushing etc, etc, nothing works so im trying to figure out how much to use in a gallon of water to drop the ph 1 point. it's CIL brand but doesn't give much info as to mixing or how much it drops the ph. just says 3/5 tsp per liter of water to change hydrangeas to blue. that doesn't help me much when it comes to MJ lol.

What method was used to determine the pH of the grow media?
Anything outside of a slurry test, or a higher end soil pH probe will give widely ranging, thus inaccurate results.

Grab some pH buffer like the stuff from General Hydro. The stuff from Advanced is way more concentrated and harder to work with. Use a good pH pen to measure the pH of the feed mix. Titrate buffer while mixing until you hit the desired pH level.

Yeah I'd start with making sure you're getting an accurate measure of your PH before you go trying to adjust it even more...you may end up surprised...as chip green said, soil PH probes work but they're simply not precise unless they're a high priced high caliber one. I'm sure they can give neighborhood measurments, but sometimes neighborhood measurments aren't enough.

Logan Burke said:

Yeah I'd start with making sure you're getting an accurate measure of your PH before you go trying to adjust it even more...you may end up surprised...as chip green said, soil PH probes work but they're simply not precise unless they're a high priced high caliber one. I'm sure they can give neighborhood measurments, but sometimes neighborhood measurments aren't enough.

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YES. Excellent post.

The soil pH probes that have the long skinny metal rod and cost like 15 bucks are garbage. I have seen them read completely wrong, saying alkaline when it was acidic lol. I have an Apera digital with a spear probe and a Hanna with a spear probe, they both read accurate on soil just make sure it's moist. The Apera is my favorite.

That's exactly what I was getting at, expecting a runoff pH, or the twopronger reading....
Many times we will hear , "ignore pH in soil"...While there is an element of truth to that, that's assuming a quality soil, with a bit of a living balance.
I use a Blulab Leap pH probe. Fox Farms claims a 6.3 for Ocean Forest. I've seen readings, out of the bag, as low as 4.8
Too many "cookie cutter" determinations are made based on soil pH.
I've had a few beers, so at this time, I will resist the desire to post a lengthy, and repetitive dissertation regarding accurate pH measurements in soil container gardening, for indoor Cannabis cultivation.

I was running Sunshine peat based mix for a while and suddenly the mix pH changed and went way up out of the bag it was over 8. Had to change brands, turns out they changed their peat moss supplier and that was the reason for the high pH. I always check now before I pot. I switched to Berger BM6 and it's working great and it's cheaper. I know these are peat based soiless mixes but it shows that pH can change from the supplier.

Oh yeah, FFOF is all over the place. Wide swings from bag to bag. Same with Happy Frog. Totally understandable, huge batches, could be mixed with any number of different batches of amendments, from coast to coast.
I've had far, far better results with the Roots Organics 707.