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About Phosphates... (long)

1109 Views 2 Replies 3 Participants Last post by  Hoppy
Like a lot of people, my tap water contains phosphates. From what I understand, it's the result of the water company and the various things they add, or the breaking down of various things they add.

I'm no chemistry expert.. far from it, but I recall reading something a while ago regarding phosphates. Because of what I *think* I know, I've made assumptions. I would like to get a "fact check" so to speak...

Macro fertilizing is NPK... Nitrogen, phosphorus, and potassium (feel free to correct me if I'm wrong. That's why I'm posting it)

In moderately planted aquarium, I ran two tests. Nitrate and Phosphate. Neither test has been calibrated to ensure accuracy, however, I did test my RO water (not used in the aquarium) to ensure that 0 was 0. It was.

The nitrate test showed around 10 ppm. The tanks is pretty well stocked. The test was done at the end of the week before their 50% water change. The amount of nitrate the test showed wasn't as important as the fact it showed a presence of nitrates.

This tells me my plants have more than enough nitrogen for the time being. This number has been going down and I'm going to keep watching for signs of nitrogen deficiency as a couple of new plants grow. (Again, correct me if I'm wrong)

The phosphate test showed a smidge under 0.5 ppm phosphates. Based on the nitrate test, I at first though "Ok, plants have enough phosphorus" Then I recalled something I read about an algae filter in a salt water aquarium. Someone said something to the effect of: There are two kinds of phosphates. Organic and Inorganic. The protein skimmer removes one, the algae removes the other. That got me thinking...

I tested the tap water, it tested at an even 0.5 ppm. Again, the actual number is meaningless since the test kit isn't calibrated, but it was slightly larger than the test of the aquarium water. I was also lucky enough to be cycling another aquarium with fish food (no fish, just dumping in food so it rots and produces ammonia) Assuming fish food introduces phosphates, I tested that and it was between 5.0 and 10.0 ppm. Assumption confirmed since fish food was the only thing being added to the aquarium.

My conclusion from the series of tests is as follows: My tap water's phosphate content is primarily composed of phosphates that are unusable to plants, the phosphates being introduced from feeding the fish are all being consumed by the plants, I should start dosing phosphorus are the normal part of my NPK dosing.

I know, I could of just posted my conclusion and not had a bit long winded post about rudimentary science, but I like to show my logic behind arriving at such conclusion. So, the real question is, am I right or wrong?

Thanks for reading :)
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