Phosphates through RODI?

VBMike · Jul 26, 2015

Hi Randy! Thanks for all you do for the community, brother!

I've got another for you.

I've been battling endless hair algae in two different tanks despite low phosphate/numbers. I maintain .06 ppm PO4 and 1 - 2 ppm NO3 with carbon dosing (Red Sea's NO3PO4-X). I've replaced all of my RO/DI cartridges in the last 3 months. I feed moderately with well-rinsed PE mysis.

The common response on the forums is "the algae is consuming the phosphate". I buy that, but I also clean it off the rocks with a toothbrush so there isn't a lot of mass to the algae most of the time.

Anyway, I understand that organic phosphates do not read on test kits. Is it possible that they are passing through RO/DI unit? It seems that that is the only logic conclusion. If that is the case, how can I combat that?

Thanks my friend!

Homer Allman · Jul 26, 2015

Test your water for phosphates before you mix it with your tank water. That will answer your question about phosphates coming through your RO/DI water.

VBMike · Jul 26, 2015

I'm sorry, I should have included that I have tested the RODI water and the fresh mixed salt water and both turn up zero. My understanding is that organic PO4 will not show up on the test, though...

Homer Allman · Jul 26, 2015

Sorry I did miss the part about some forms not reading on the test. I am/was fighting some of the same issues. Have you read anything about peroxide dipping your rocks? It works magic on algae.

VBMike · Jul 26, 2015

Yes, thanks. I did that on one of the tanks and it did work, but it came right back.

The other issue that I have with it is that it also appeared to kill the rocks that I dipped... they turned white and went through a diatom bloom as they re-cycled.

Homer Allman · Jul 26, 2015

I nuked mine pretty hard and they didn't turn white. We'll see if anything comes back. I think there are lots of nutrients hiding in the sand bed that could be feeding your algae. How big is your tank?

redfishbluefish · Jul 26, 2015

I've heard of treating an entire tank with peroxide (ml quantities) but never rock...unless you wanted to use peroxide instead of bleach to kill the rock. Once you peroxide dip rock, you have dead rock and now need to first cure and then cycle the rock. During the curing process that rock will put out nitrates and phosphates....the remnants of everyting the peroxide killed (and a pretty good stink). This could take up to four weeks or more. Measure nitrates and phosphates while curing and do water changes as needed. Keep a heater in with this rock and have good circulation with no lights. Typically during the curing process, cycling will begin. Here you want to look for ammonia. To accelerate the cycle, after about four weeks, add one of the bacteria products they have...such as BioSpira.

Homer Allman · Jul 26, 2015

The peroxide dip was to remove pests and kill the algae. I mixed a gallon of peroxide with 8 gallons of saltwater. I dipped for around 2 minutes. The worms rolled out and the algae is leaving. I agree with recycle part due to the things it killed inside. Worms and algae had to go though. My test rocks never looked better.

VBMike · Jul 26, 2015

The SPS tank is a 75 and the other one is a 14g Biocube. To the sandbed point, I just moved the 75 in May and completely rinsed the rock/sand and gave it an 80% water change. I also tore down and cleaned the Biocube in June with a 100% (!) water change. I think the large water change problems are greatly exaggerated, but that's a different conversation.

Bottom line is that I'm pretty sure the algae isn't from husbandry issues... I obsess over my tanks, lol!

Randy Holmes-Farley · Jul 27, 2015

The RO/DI isn't a significant source for you. Your foods are. Nearly all of the phosphate in food ends up in the water available to algae, whether it is immediately eaten by something else or not. An adult fish for example, will excrete all of the phosphate it takes in, and a juvenile excretes most of it.much about organic phosphate as a source, although it might be in some cases.

I wouldn't worry much about organic phosphate as a source, although it might be in some cases. 0.06 ppm inorganic phosphate is far more than needed to support rapid algae growth.

VBMike · Jul 28, 2015

Thanks. I've seen your phosphate comparison of foods, but I think that was a little dated by the time I saw it.

Generally, do you think that pellets are lower phosphate than well-rinsed PE mysis?

I know correlation does not mean causation, but it seems like there's an algae bloom after water changes. And the pre-filter cartridge on the RODI is tan after running 40 gallons and brown after 80 gallons. Interestingly, this is municipal water source.

lisawolk · Jul 28, 2015

Homer Allman said:
Test your water for phosphates before you mix it with your tank water. That will answer your question about phosphates coming through your RO/DI water.

My thoughts exactly!

VBMike · Jul 28, 2015

As stated, RODI tested zero. Organic phosphates do not show up on a test, though.

Randy Holmes-Farley · Jul 28, 2015

VBMike said:
Thanks. I've seen your phosphate comparison of foods, but I think that was a little dated by the time I saw it. Generally, do you think that pellets are lower phosphate than well-rinsed PE mysis?

I know correlation does not mean causation, but it seems like there's an algae bloom after water changes. And the pre-filter cartridge on the RODI is tan after running 40 gallons and brown after 80 gallons. Interestingly, this is municipal water source.

I've not seen newer info on phosphate levels in various foods, so I don't really know.

If you get a bloom after a water change, that might be due to algae being limited by the availability of a trace element such as iron from the salt.

Cory · Aug 4, 2015

Algae is an indicator of po4, and nitrogen someplace.

The biggest places ive read about and found to be true are food and the sand bed.

All that food you put in stays in. Thats a lot of algae food eventually unless that food in comes out some way. Ever seen a dirty carpet? Thats a lot like sand. I love the look of white sand, but wont use it in my tank because it traps amd pollutes too much.

This is why i painted the bottom of my tank with "sand spray paint". Its on the outside and looks similar to sand. I run a bare bottom tank.

The other source of organics causing algae to grow are unregularly washed filter socks and chaeto collecting organics. But the bottom line is you must keep a clean tank or build an ecosystem that maintians it. The latter is harder to do.