I'm not sure but I believe sulphur is not too good for plants.
you could use vinegar or lemon juice to lower the pH.
I believe greystoke recommends waiting like 24 hours after adding to allow the carbon out of solution so the pH will stabilize.

Ooops. I made a mistake. It was aluminum sulfate, not amonium sulfate, the nursery sold me.

Well, it was taking a ton of vinegar to get it down so that's why I went looking for something else. I didn't think of lemon juice. Maybe I'll try that this weekend instead until I hear from someone whether the "aluminum sulfate" is acceptable. Thanks.

Connie

Vinegar is a weak acid. If it doesn't work in your case I suggest that you buy some battery acid (=33% sulphuric acid) from a garage and dilute it ±20 times with tapwater (careful! That stuff is dangerous. Wear goggles and gloves and perform the whole operation in the sink) eg: pour 50mL acid into ±1L of water.
The diluted acid works well as a pH-down.

Good luck

Thank you, Greystroke. I'll try that. Connie

I'd use citric acid or something like that in a pinch, but I'd never use battery acid. I try not to feed my plants anything that isn't manufactured specifically for human consumption or for growing plants for human consumption. Maybe if I grew ornamental plants or something, but I won't waste hydroponic space on flowers.

True hydroponic pH up and down is lightyears ahead of the DIY stuff because it has buffering agents included that allow it to not only effect a change in pH right now, but to help hold that change over the long run. If you use straight acids like coffee, lemon juice, and so on you'll often find that a few hours later your pH has jumped back up.

Real hydroponic stuff is worth the time. You can order it online and have it shipped to you if there isn't a local place to buy it.

Here is a link that might be useful: Here's where I order