Yes, I, Bill Cody and Instar say something isn't right with the 200 ppm you read. Either it was micrograms/liter, it's a typo, or flat out wrong.
AES says in their catalog that iron as low as 0.15 ppm can be fatal to fish. I can tell you from personal experience this may be true in some cases, but with myself and my overall water chemistry it's not a problem. My RAS systems routinely run about 0.25 ppm and the fish are fine.
The sharp edged precipitate can collect on the gills of small fish and cause irritation but larger fish aren't as effected.
Stoney Creek Equipment company in Grant Michigan used to hatch their own trout (they may still do so) and they told me they have actually had it collect on the eggs with no problems. They also told me after about 4 inches the trout gill filaments seemed to be course enough to not be as sensitive.
One thing to keep in mind also is iron bacteria will break down the iron in a pond. Even though my trout pond received iron at about 2.5 ppm it dilutes down to about 0.4 ppm. Not sure if it's all dilution or some of the it is iron bacteria breaking it down as I see lower iron levels in the pond in the summer when the water is a little warmer.
The reason I am skeptical about iron tests that are sent off is I sent one off and it came back much much lower than the actual iron level. In fact it was almost undetectable according to the testing firm when I knew it was in the 2.5 ppm range.
Last edited by Cecil Baird1; 05/04/12 09:16 PM.
