View Full Version : Is my homemade fish food causing high Po4?

07/12/2017, 08:34 PM
My phosphates were really high at 2 a few months ago. Started using more gfo and a small bag of phosguard along with more frequent water changes and got it down to a steady 0.6 (still really high). Also have a algae scrubber and lots of macro. Tested today after about a week of no testing and it's up to 1.07. Water changes do nothing. I have been feeding with a homemade mixture of different frozen seafoods rough chopped and frozen in rodi. I tested a VERY diluted sample of fish food water and the vial turned dark blue using a Hanna checker. Didn't bother trying to read it. Would a frozen food just normally show high phosphates and the small amount fed would be so diluted by the time it got into the tank or does this sound like the source?
125 reef btw

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07/12/2017, 08:43 PM

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07/12/2017, 09:01 PM
If the food is the cause,and had been used for about 9 months, could the phosphates bind to the LR and sand ( making it hard to get rid of) or should a discontinuation of the food and water changes do the trick?

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Ron Reefman
07/13/2017, 04:12 AM
Before I'd blame the homemade food, I'd try some frozen or liquid fish food sold at an LFS. I've never had an issue, so I've never tried it. But I wouldn't be surprised if the test turned out very similar to the test of your home made food. Then again, maybe it will be very different and you'll know for sure.

If you do try to test some commercially prepared fish food, I'd be interested in your results. Or maybe others here have tested some and can help out.

Sorry hegeh, but "Bingo!" just didn't satisfy me as an answer.

07/13/2017, 05:15 AM
Your test was a good idea. It probably does not provide an accurate description for the phosphate content.

Better to look up (Google) % phosphorous in the foods you are using and the weight you put into the aquarium everyday. You might just be feeding too much.

Another comparison to make is to look up phosphorous content for commercial food so that you can get a feeling for how different your food really is. Might not be very different.

Diagnosing the cause of algae growth is not as simple as a phosphate reading, but it is better than nothing and a good start. The fact that you have lingering phosphate means that you are not using an adequate amount of GFO to keep the phosphate level down. It might take quite a bit more than you are using to lower the phosphate level.

My approach would be to confirm that you are not overfeeding (not so simple and don't starve your fish) and get a feel for the phosphate level of the food you are using. I would not change anything without being well informed. And starting now, increase the amount and frequency of changing the GFO. You might try doubling the amount of GFO and measure the phosphate level after a couple of days. Let the results guide you on how to proceed with amounts and frequency of changing the GFO.

07/13/2017, 03:43 PM
I agree that checking the feeding amount is a good step. Some foods will contain more phosphate than others, and leaching can vary a bit, too, I suspect. You could try using a binder like gelatin when making fish food. That's what I did. That might reduce the leaching factor some. I haven't done any measurements, though.

You could try comparing the leaching from the food you made to that from a commercial mix, if you're interested. A lot of liquefied ingredients could cause more phosphate in the water column in the short term. In the long term, there are a lot of factors at work.

Big E
07/14/2017, 04:02 AM
I'd read this for some help--


Most raw sea food should be low in phosphate, but you also have to consider what a store may use as preservatives. Tripolyphoshpate is commonly used........I have no idea how much that would actually add in phosphate.

I would also suspect your GFO is getting exhausted in a week or less with those high levels you're trying to knock down. You may want to try to change it out more often or at least track/test your reactor output levels over time to get a better handle on when to change it out.

If you get down to .10 ppm or less it's likely you will only have to change out the GFO on a monthly basis.

I use half the recommended amount changed monthly and can keep P04 at around .05-.07 ppm per a Hanna 736.