Thanks DDon, I've definitely noticed the uselessness of the 200 micro socks. I've read that the dinos are between 10 and 20 microns so I've ordered some 5 micron socks like you suggested. Also the only UV sterilizer I could get at my LFS was the turbo twist 12x. I don't think it's powerful enough to link in to my return pump (i run at approx 1200 gph). So what I've been doing it suctioning as much as I can off the rocks during the day and then returning the water back through the turbo twist at a slow rate (approx 150 gph) with the hope of killing all the dinos on their way back into the tank. However, I have sampled this water and there were still live dinos present.
I've spent the last couple days researching UV sterilizers and I think I'm going to go with AquaUV. They have good reviews and I can get it through a Canadian on-line distributor. I'm just trying to decide on size. I don't need it to kill protozoa so from the info that's available I believe I need one powered to 30,000 µw/cm2 at 3-4x tank turn over per hour, so 30 000 at 1600gph to be safe. From their website the classic 40 watt fills those numbers. However I don't want to spend all this money and not have enough power so I think I'm going to go with the classic 57 watt at least. Also I'm going to get a DC return pump to optimize this flow rate. Overkill? Perhaps, but given the time and effort and $ I've put in over the last 10 years I feel it's something I need to do.
Also, just and update. I've been dosing seachem nitrate and phosphorus for the last few days and things have gotten worse. I know it's going to take some time, but I sure hope it doesn't get much worse than this.....