Phosphates?

[Andres391]

So my tap water has 0.25 phosphate and fertilizer has 0.14 phosphate which I'm light dosing with half the recommend dose of course fish food which I feed once a day and organic waste so has any one have used distilled water and reminerlize maybe with fertilizer and little bit of aquarium salt or just stick to the water changes with tap water isn't better to go with water without phosphate?

 

[awilkinson871]

Almost all tap water is going to have phosphates in it. The only time it is an issue is if it is causing massive algae issues.

 

[GlennO]

I don’t see any need to restrict food or use alternative water.

 

[CrackerboxPalace]

For the typical freshwater aquarium fish, phosphate compounds can be harmful, especially above 1ppm. So keep an eye on it, but it shouldn't be at zero because your plants need it. It would be best to use a different, phosphate free water source.

Aquatic Toxicity Assessment of Phosphate Compounds

50% lethal concentration (LC50) was >100 (measured:>2.14) mg/L and >100 (measured: >13.5) mg/L, respectively.

 

[JTW]

For the typical freshwater aquarium fish, phosphate compounds can be harmful, especially above 1ppm. So keep an eye on it, but it shouldn't be at zero because your plants need it. It would be best to use a different, phosphate free water source.

Aquatic Toxicity Assessment of Phosphate Compounds

Reading that article, it appears that 1ppm would be well below the safe limit. At least for the two substances that they tested.

"The results of the ecotoxicity tests of tricalcium phosphate and calcium hydrogenorthophosphate are as follows: In the acute toxicity tests with fish, the 96 hr LC50 was >100 mg/L (measured concentration: >2.14 mg/L) and >100 mg/L (measured concentration: >13.5 mg/L), respectively."

"The results of the fish acute toxicity test showed that no mortality or adverse effects were observed at control or 100 mg/L (nominal)."

In their tests, the measured concentrations of their test substances were 2.14ppm, and 13.5ppm. They observed no mortality or adverse effects. Granted, the test only lasted 96 hours, and they only tested 2 types of phosphates. So we can only draw limited conclusions from it.

I have read the 1ppm limit for phosphates before. But I've also read 3ppm. So I wonder if those figures have come from rigorous testing, or simply caution.

 

[GlennO]

Some keepers of heavily planted hi tech tanks run PO4 at 5-7 ppm for optimal plant health (EI dosing). Every tank is different but 1-2ppm is more normal for most planted tanks with an approx ratio of 1:10 (PO4:NO3).