I'll pass on either or, as I have done both, and I am more comfortable with gypsum application. It also gets me the hardness that I need in my hatchery pond soft water.

I can't remember if it's been addressed, but what about application costs when dealing with alum/hydrated lime? If we're talking about a pond that's big enough to require a boat/barge that can handle a chemical application X 2, what and how would the price affect the overall cost? Kenny, I would think you, Rex, or Scott would have a good feel for it. Of course, mileage $ would have to be left out since it's always a variable.

If one does go the alum/hydrated lime route, then I can't emphasize the care that is needed when applying the lime. Stay dry and have PPE for both eyes and face. I use a 3M Rugged Comfort Quick Latch, and dispose of the canisters after usage. I like this one because it's great protection, sizable, very comfortable, and it allows you to hang it around your neck while you're getting ready.

Story 1) When I was young and handsome(40 years ago), I was carting a pt into the emergency room at Parkland Hospital. Once we were inside, we passed a treatment room, and it had 1 ER dtr, 1 Burn dtr, and 3 nurses cutting the clothes off a man. Turns out he was burnt by hydrated lime while adding it to concrete. He had 1st and 2nd degree burns from the neck down, and was obviously in pain. The potential future debridement would only make the pain worse.

Story 2) I have a neighbor that was in concrete and road construction for close to 45 years. He was prepping soil for a pad that was a continuous pour, and they used hydrated lime to help dry up the soil before the pour. The HL dust got in the cab of the equipment he was on, and got it in his eyes. He bleed from his eyes, had impaired vision for a short time, and was lucky there were crew members close enough to help him flush his eyes. IIRC, he said always kept vinegar and water jugs in his truck in case of hydrated lime burns. His vision got better, but it was a very close call.

So, I don't mean for this to be a "Christmas Story" you'll shoot your eye deal, just be careful. When wet, hydrated lime deserves all of our respect.

AL