Alum, borax, etc.

[waterbear]

That's an interesting one. Percarbonate is the principle ingredient in color safe bleaches. (The other principle ingredient is another old pool friend, sodium carbonate.) I remember seeing it at a chemicals store I've used for photo chems: http://www.chemistrystore.com/search...+to+Search.y=0

It sure would be a lot easier to scoop off the top than the bottom, like with alum!

Any info on dosages, downsides?

It's actually the main ingredient in oxyclean (at least the original one) and when dissolved in water forms sodium carbonate and hydrogen peroxoide.l Most oxygen bleaches are also persulfates and perborates, however.

To use sodium percarbonate on a badly fouled pool (in other words, a swamp with lots of stuff on the bottom!) broadcast 10 lbs per 100O gallons with pump OFF. Immediately broadcast 3/4 lbs dry acid per 1000 gallons to keep pH in line (since the pump is off using muriatic acid is trickly as it won't disperse thoughout the water. As debris floats to the top skim it out. When debris floating to top stops run pump for 24 to 48 hours, clean filter, and vacuum if needed. If pool is not clear repeat process. Because of the amount of percarbonate and dry acid needed this is not a cheap process but is it a fast process compared to trying to clear the pool with just chlorine. Percarbonate can also be used to convert a biguanide pool to chlorine at a rate of about 5 lbs per 10 k gallons ( or 1/2 lb per 1000 gallons) and the dry acid si not needed but pH will need to be adjusted afterward when the chloirne is added once the biguanide is fully oxidized and the filter medium changed out.

[PoolDoc]

To use sodium percarbonate on a badly fouled pool (in other words, a swamp with lots of stuff on the bottom!)

If you do this, next spring, I'd be grateful if you'd do pictures and record doses and results.

I've done something similar in the distant past, but we don't have enough info to know exactly when and how to recommend it.

[waterbear]

My pool stays open year round and never turns green and I am not working on other people's pools these days.

[PoolDoc]

Yeah, that's sorta my problem, too.