Just to be clear, by clogged you don't mean lack of flow, but clogged media. Because flow has been good through this whole ordeal. These tiny snails, however, have infiltrated every little available space in the foam and the bio-rings. I don't believe poor water is the cause of this problem as I am very diligent with 40% weekly changes. I believe , rather , the poor quality is a result of the infestation. I have 3 other tanks on the very same maintenance schedule and they are in good condition. I tried everything I could to save these fish. The only thing I didn't do was clean the filters because I didn't want to remove any of the bacteria. I guess the snails did that anyway. I did everything I could possibly do to correct the problem from a barage of medications to large water changes and even added a UV sterilyzer. I am relieved , actually, to have found these pests. I thought I was doing something to poison these fish but I now know what the difference is between this tank and all the rest. SNAILS! Once I've gotten rid of most of them my loaches should take care of the rest after I get the tank up and going again. I have been banging my head against a wall for over a month trying to get to the bottom of this. Asking myself several questions only to come up with the same answers over and over again. I thought maybe there was something wrong with my water treatment- but I use the same treatment for all the other tanks. That couldn't be it .
Maybe I got some kind of airborne contaminate- but why isn't the other tank having the same problem?
I even tried to lay blame on the FX5 filters because that was the only difference between the 230 gallon and all the other tanks ( which are filtered by AC filters).
With 15 yrs in the hobby I haven't experienced anything quite so enigmatic. This hobby is always teaching me new things . The amount of articles on disease and treatments that I've read in the past month ,searching for a cure , is staggering.
One conclusion I can definately make is that there are a lot of meds out there that treat symptoms but the key is to find the trigger and I believe I have done that. I currently have no scientific proof but I'm confident that once the snails are gone so to will be my problems. I expect to hear a bunch of people come in and tell me that they actually use these snails to help keep their tanks clean and in smaller numbers they may be effective but not when they become a plague of locust-like proportions.
Lastly I'd like to thank you Robin for your expert advice and kind words. If you have anything else to add or if any of this information appears misleading or incorrect please post so we can help somebody else if they encounter similar problems. Losing a tank full of fish that took over a year to collect and grow out is not something I"d wish on anyone. It truely is heartbreaking.