"scs0" wrote in message
oups.com...
My pond is made from an EPDM liner so concrete construction is not an
issue. I'm glad you asked about the tap water pH because I forgot to
mention that, I tested the pH last week and it was in the 7-8 range. I
forget what it was but it was something pretty typical like 7.2 or 7.4.
Over the weekend I finished up some work on the pond and filled it
with an additional ~400 gallons or so of water. This was a combination
of tap water and rainwater that poured on Saturday and I'm still having
problems.

I'm not sure what my sand's pH would be, I'm not right on the coast
but I suppose the entire peninsula was right on the coast at one time
or another. I would love to use clay soil. Up north I saw some native
ponds that had a clay bottom and the smooth heavy texture seemed
perfect for aquatic plants but I haven't been able to find clay
anywhere. I've tried big outlets like Lowes and Home Depot. I've
tried smaller nurseries, I tried two rock & gravel yards, and I've
tried water garden speciality places and nobody sells clay. I always
read about people using clay for aquatic plants but no one ever reveals
the secret on where to buy it! I'm afraid of using kitty litter
because I don't feel secure that its added perfumes and other additives
would be safe in a pond with plants and fish.

I tried an aquatic plant soil once, I think it was Scotts, and it was
horrible. I had expected it to be granular clay that would disolve
when wet, but the light chunks didn't dissolve at all. It was like
trying to pot an aquatic plant in styrofoam balls. The stuff was too
light and therefore had pitiful holding power. I can't believe its
still on the market.

Oh, and my pots aren't completely sand. I noticed that gravel always
seems to sink into the planting medium so since gravel makes an
adequate potting medium I mixed gravel into the pots. (It's probably a
75% sand to 25% gravel ratio though)

Hmmm. I suspect that it may be the Florida sand you are using, but I could be
wrong. You should check the pH. If you don't have a pH kit for soil, you can
take a fresh sample of the sand (not from the pots), and mix it with tap water
in a small glass or jar (check the pH of the tap water first). Let the mixture
sit for a few hours (one day might be better), then check the pH of the water.
If it is in the same range or higher than your pond water, you've likely found
your culprit. You can use bentonite clay as a substrate for plants, which you
should be able to get at the building materials section of Lowes. Sometimes it
comes in bags like concrete, and sometimes it comes in 5-gallon buckets. It's
pretty cheap. Oh, I almost forgot. When using bentonite, it is a good idea to
mix it with water in a small tub or other container. Mix it a little at a time
because bentonite absorbs water like crazy and will swell to 20 times its dry
volume. I have mixed a cup at a time with good results. The stuff will be very
slippery and icky to touch. Once it has completely swelled as much as it is
going to, then you can mix some gravel in with it and then plant your plants in
the pot you are going to use, using the bentonite/gravel mixture for the
substrate. Good luck.

~George~
________________________
Here is a quicktime movie of my albino catfish beeing fed last year. He's much
bigger now:

http://home.insightbb.com/~jryates/catfish_eating.MOV