Phosphate mystery

[Jim Miller]

I'm not having a phosphate problem just a mystery. My phosphates are above 10ppm in spite of not dosing for them. I dose KNO3, K2SO4 and CSM+B and occasionally extra Fe/EDTA. Plants are growing like crazy with 4x T5NO and ~30ppm CO2!

Although I follow the EI prescription for dosing, I test before a 50% (well) water change just to see how the uptake is of NO3 and PO4. Lately with the increased bioload I also test for NO2 just to make sure I'm not poisoning fish.

I stopped dosing KH2PO4 when I discovered that my phospates were well over 10ppm prior to a water change. I figured that with a 50% change they would drop to only 5ppm which was still plenty. Imagine my surprise when after a week they were still over 10ppm.

My guess is that they are coming from the feedings I'm providing. I feed mostly frozen foods: daphnia, rotifers and brine shrimp. I also do some Kens flake.

Any ideas?

Jim

[Ben Belton]

I fine it hard to believe that that much could come from the food, but who knows. Did you test your well water?

I've worried about putting too much PO4 in my tank and recently with caution and concern upped the amount to around 2ppm. After reading this, I'll stop worrying about having too much now.

[Jim Miller]

I'll test my tap tomorrow.

Thanks!
Jim

[Jim Miller]

Just did some testing: tap and reservoir tank both show 0.0ppm phosphate.

I also put some K2SO4 that I've been using in place of KH2PO4 to maintain K+ while waiting for P to drop. I did that in solution to make sure it wasn't contaminated with P in some fashion. Test showed 0.0ppm of PO4 in that solution as well.

So it's definitely in the tank rather than being added through the water.

I probably should check a KNO3 solution and CSM+B solution just to make sure those don't have a PO4 source.

Jim

[150EH]

Jim you posted the question about stocking the other day so with a more than healthy fish load maybe you don't need to dose EI anymore. I went back and took a look at the thread and you quoted 97 fish with most of them being smaller varieties and 72 shrimp plus snails, so poo may be all you need.

I would try a light vacuum over the substrate to get any fish waste that has not started to break down any cut your EI dosing back gradually every week or two until you find a comfortable level.

I'm certainly no expert and just trying to come up with a good guess.

Another good possiblity is your test kit is off?

[Jim Miller]

I know I'm committing EI sacrilege but I test my water before each Sunday's water change to get a feel for nutrient uptake in addition to watching how the plants are growing. It's this way I know how I might want to bias the EI prescription. I've seem that if I miss a day or two of nitrates they plummet. I dose K in proportion to NO3.

I plan to measure PO4 tomorrow then do 2 water changes to see if the concentration drops in the expected proportion. Then I'll track daily through the week.

Fun stuff!

Jim

[150EH]

I only test for nitrates anymore and on a weekly basis with a Mardel 5 in 1 dip strip of all things, but I haven't tested for anything else in some time. I just got frrustrated with these cheap test kits and found that most were junk, I have a RedSea kit that I use to sit my DIY bubble counter on because my CO2 line was too short after I upgraded to a 10# tank, so I don't think much of it.

I did get courious as to what could be making your phosphates rise but only found this, good luck.

Where Do Phosphates Come From?
Phosphates naturally occur as wastes are broken down within the aquarium. In addition to being internally produced, phosphates can enter the aquarium from external sources. Everything from food, to the chemicals used to buffer the water, to the water itself can contain significant amounts of phosphate. Phosphate sources include:

•uneaten food

•plant decay

•dying algae

•fish feces

•dead fish

•carbon filter media

•aquarium salts

•pH buffers

•kH buffers

•water itself