Bill if you have a natural or fertilizer induced plankton bloom then trying to clear the water of plankton with alum or gyp. for esthetics is at cross purposes (clear water vs. fertile productive water) and may not work as per the above link. Cooler water temps will usually reduce the plankton bloom's density and the water will clear. Water quality is very important to all pond goals whether you want green water with lots of fish growth or gin clear water for swimming. There is info here on the subject and a series of PB mag articles in progress on the subject. Learning about how your pond water works is an interesting journey and is unique to your pond. It takes time and knowledge to understand how it works and responds to what you do. Good luck and post what you see and do and how it works. After about five years I began to have a good feel for our ponds and how they work and react.
Thanks for the reply. You are right the plankton bloom will fade some in the winter. It usually has a green tint until I start getting a lot of rain and there is an overflow. In normal years there is a lot of overflow for several months. Then the ponds water looks like a clear black. But if you stick something under water it has a red ting. As I said when the pond was first built before it received any run off it was just a pit that in the center and around some of the island had ground water. Before the first run off without fertization it turned a real pretty tropical looking green. When it got the run off it did turn muddy and I did add a little gysum, not much only a very small fraction of what was recommended. The contractor had problems finding places to put all the dirt they took out and on one sloping side they put white looking sub-surface clay that was rock hard. I spread hay along with seeds over that area but also put some gypsum on that to soften the soil. That soil is still real hard still but eventually went through the disburbed ground cycle of tall weeds to grasses. And mostly now has native grasses like little bluestem and a mix of others. But I have read to really loosen up the soil you need to treat it with gysum three years in a row.
Anyway to get back to the point I think I could have a clearer water (not considering plankton) just from suspended micro suspended paritals of red clay which more than half of the pond bottom is and all of the dam. The gysum could get rid of that, then I'd fertilize to get a bloom again. Like I said the pond by the end of winer will have had a lot of turn over and usually never gets a bloom until I do fertilize except for that first year. In fact this year we were getting a lot of rain even in July and overflow and I lost my blooom and added a small amount of liquid fertilizer around the end of July, and it brought the bloom back.
So I guess it really all boils down to the clarity of the water is effected by two things, micro-suspended clay particals that I want the gypsum to get rid of during a time when there is not a plankton bloom and when all fertilizers have been washed out of the pond. Then when the water gets warm enough to fertilize get a plankton bloom that will reduce the water clarity in a good way which will probably as I have seen in other places produce a nicer looking green when the plankton is over coloring the blackish red ting. The gypsum won't keep clearing everything out of the pond forever and since has some kind chemical attraction to the suspended clay particals I don't think it would clear out plankton anyway, or don't think from what I have read. But it should be long gone before I fertilize in the spring.
I have until the end of next winter to decide for sure. I am getting the water test this weekend and maybe the lime will do the trick without the gypsum.
