just read your thread with great interrest. I've installed a small (120gal.) preformed pond to fill a spot. I've had it for about 1 1/2 years now and even though I've had water-plants (lilies, grasses, hyathinths and salads) from day one I've had to empty and clean it about every 8 weeks.
The pond is in full sun, I planted small shrubs and flowers to accent and shade it as well. The gold-fish in it seem to be doing fine, but the nasty looking and smelling algae problem seems to recurr no matter what I do.
I've tried the 'blue stain' to reduce UV exposure, chemicals that's supposed to 'clump' algae when it forms and all sorts of other things. I like the tranquility it gives us, it has a small (~100gph) pump to circulate the water.
I'm not sure about the UV-bulb you described earlier,does this sit by the pump in the water?
I also have seen larger filtration units at the local store, would this help alleviate the problem?
Any additional input would be appreciated.
If it ain't broke you aren't trying hard enough