Phosphate dissapearing act.

[dales]

Hi guys,

Im in need of your advise. Ive start dosing phosphate recently as my tank is not showing any phosphate reading on my API test kit. I know test kits are not 100% accurate. I dose 5ppm phosphate to a 20L tank with 2 x 23w cfl. Tank is not heavily planted and test the waters again after 1 1/2 hours later and test kit shown a reading of 5ppm +/-. After 23 hours, i tested again and the phosphate is gone. Any idea whats the cause? I dont think it precipating as i dont see any cloudy waters or flakes. I maybe wrong though. Below is the picture of the tank.

Please help. Thanks!

ImageUploadedByTapatalk1413966366.258039.jpg


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[Urban Aquaria]

Its possible the phosphates have simply be taken up by the plants... 5ppm is an okay amount which should easily be consumed quickly by the various plants in your tank, especially since your tank has Co2 injection and sufficient lights.

One thing with the API phosphate test color chart is that although the 5.0ppm measurement has a very distinct dark color, when it gets to 2.0ppm and below, the colors start to become abit difficult to distinguish, the tone of the yellowish color start to get affected by ambient light and background, can look more greenish at some angles while at some other angles can look more yellowish. When i use that test i just assume any yellowish color could be between 0-2ppm.

I guess as long as your plants are not showing phosphate-related deficiencies and algae is not going crazy in the tank, it most likely means PO4 is at ideal levels for the plants to utilize and grow.

[dales]

Thanks for the advise UA. Ive increased the dosage today. Will update if the phosphate is still in the tank tomorrow.


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[dales]

Hey guys, an update. I double dosed phosphate and today tested the water only to find 0.5ppm left. Is it possible that the plants absorbed that much phosphate over a period of one day?


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[Urban Aquaria]

Looks like your plants are probably soaking up the available phosphates and storing them for usage.

Your tank also looks to have very minimal livestock, i only see a few shrimps on the plant leaves and a snail on the glass, i'm guessing they only get fed lightly? That probably explains the lack of constant natural phosphate generation and the need to dose more of it to supplement the plant requirements.

In my experience, a large portion of phosphate in most planted tanks comes from the livestock bio-load and the food fed to them, commercial food and the resulting waste production seem to generate alot of phosphate content. In my planted tanks with moderate bio-loads of fishes and shrimps that receive regular feeding, the phosphate levels usually seem to hover consistently at around 1-2ppm, so i rarely need to dose extra phosphate ferts (unless the bio-load and feeding are drastically reduced).