Pond Boss Forums INTRO Questions & Observations IRON

CAN A POND HAVE TOO MUCH IRON IN THE WATER? MY WATER IS KIND OF YELLOWISH IF YOU PUT IT INN A GLASS AND IF YOU WATER THE GRASS WITH IT AND THE WATER HITS ANY ROCKS THEY TURN LIKE A RUST COLOR. IS THIS BAD FOR FISH OR DO FISH LIVE WITH THIS IN THE WILD ALL THE TIME? PLANTS DON'T SEEM TO HAVE ANY PROBLEMS GROWING IN THE POND. HAD IT TESTED ONCE I DON'T REMEMBER THE NUMBERS BUT I KNOW THEY SAID IT HAD ALOT OF IRON IN IT.

How old is the pond?

Did you just fill it with well water by some chance?

What is the water source for your pond i.e. runoff, springs, artesian well, well water etc.

Do you have any fish in it now?

Find out your ppm or mg/l iron (should be on record) and get back to me.

Answer these questions and I'll be glad to give you my thoughts and experiences with iron and even a remedy if you need one.

Keep in mind iron should be tested on site and not some time later to be accurate. I shipped a sample of my well water to a lab in Colorado and it came back as .15 ppm when in fact it is actually 2.42 ppm.

If you do get a sample for testing, you can "fix" the sample by lowering the pH below 1.5 to keep the iron soluble. If you do not fix the sample, ask for a total iron sample, which will result in them acidifying the sample prior to testing to measure both soluble and insoluble iron. You can also filter a sample at the time of sampling and then fix another sample and send both the filtered water and the unfiltered water to determine soluble vs. insoluble iron. If that is of interest.

Most well waters max. out around 5-8 ppm. It is hard to keep more than around 2 ppm in solution in an aerated water unless the pH is below 6. Most industrial NPDS discharge limits for iron are as high as 2-5 ppm, so there is likely not an issue for fish health, but the water will stain at that level. If you filled your pond from a well, then the iron levels will disapate over time as the solubility of oxidized iron is not more than around 0.5 ppm in normal pond pH waters, depending on the salt formed i.e ferric chloride is more soluble than is ferric phosphates. Keep in mind that blood requires a certain amount of iron to prevent sicle cell anemia, so iron in nature is neccesary.

Here is the section of an MSDS for pure elemental iron, that deals with the ecological impact of iron.

12. Ecological Information

Environmental Fate:
No information found.
Environmental Toxicity:
No information found.

Note that there is no ecological impact. The LD-50 on rats is relatively high, and is no where near what you would experience in natural waters.

I would not worry bout it.

Yellow water might also indicate natural tannins and lignins found from organic decay, particularly if you get run off from a forested area. Bleach the water. If the color is iron, it ill oxidize and fall out of solution. If it is color due to tannins etc. then these will be bleached out to a lighter color.

Good information M.S. It's obvious you know your stuff. My sample was not fixed and I was never instructed to lower the PH to fix it. Seems like the lab should have known better but they apparently didn't.

Iron can irritate the gills of fish but mainly fry and smaller fish with fine gill filaments in a situation where the iron has not settled out yet. As in incubators, raceways, circular tanks etc. My trout of at least 7 to 8 inches can tolerate it in a pond setting because the iron starts settling immediately after packed column areation and gravity fall into the trout pond and therefore it dilutes in the pond. I can't verify but I was told my one trout farmer anything over 4 inches should be alble to tolerate the iron although I have no idea how much iron he had.

Like M.S. I too wonder if it is iron you're dealing with.

I DO GET ALOT OF RUN OFF FROM WOODED AREAS IN THE SPRING AND SOME IN THE LATE FALL. I BET YOUR CORRECT AND IT IS THE LEAVES MAKING THE WATER YELLOWISH.
IT IS VERY OLD WOODS THAT WERE NOT EVEN WALK ON FOR AT LEST 30YEARS SO THERE IS ALOT OF DECAYING TREES AND STUMPS.
THE POND FILLED UP FROM THE GROUND AS THEY WERE DIGGING IT. WOULD THAT BE CONSIDERED SPRING FED?