Sudden Phosphate Spike

[joshbpaul]

Hi everyone.

I have a 30-gallon tank, with 6 fish, a few RFAs, and soft corals. My phosphates spiked this week, going from about 0.05 to 0.9 ppm on the Hanna checker! (They may have been higher, but that's as high as the checker goes.) A large water changed and some of the Brightwell Phospate-E reduced them to about 0.25 ppm, but they spiked again a day later. All of the major livestock (fish, urchins, bigger hermits) are alive and accounted for. It's possible there are a few snails and/or hermits that died, and are releasing phosphates, but that much? Alkalinity, pH, salinity, ammonia, and nitrates are normal, and there's no GHA or other nuisance algae. Well, at least not yet! I'm using 6 tbsp of GFO in a reactor, and added more to the media basket.

Any ideas what could cause such a sudden spike?

Thanks very much for the help!
Josh

 

[Randy Holmes-Farley]

I expect that jump is test error, either before or after the jump. The only way for that to happen is add a massive amount somehow.

I'd double check the phosphate reading before potentially driving it too low with GFO.

 

[Troylee]

Agreed with Randy.. those Hannah checkers are very touchy.. once you put the vial in and hold the button for the counter do not move the tester at all or it will give a different reading over and over…

 

[joshbpaul]

I expect that jump is test error, either before or after the jump. The only way for that to happen is add a massive amount somehow.

I'd double check the phosphate reading before potentially driving it too low with GFO.

Thanks! I'm taking a sample to my LFS to double check the results.

 

[jda]

The later-in-the-day spike was the sand/rock unbinding po4. This is a normal thing. If you do end up with 0.90, or so, in the water column, you likely have a massive amount of po4 in the rocks and sand acting as a reservoir.

 

[Guiids]

@jda Not OP, What can be done about this reservoir? I'm just now learning mine is high at 0.75 in a fish only tank. Tank has been established about 2 months but I'm worried the carribsea live sand or dead rock I'm using had/has phosphates in it.. not sure what to do to get the levels down if it's still bound in rock. I havent tried anything yet just got the checker today because I wanted to add my first coral.

Another note, I had regular flouescent lights in the tank with probably 0 PAR, algae has been very minimal just some green on the rocks. Ammonia, nitrite, nitrate all 0.

 

[jda]

You have to remove po4 from the water and the aragonie will unbind. It can take a long time. There is likely a massive amount of po4 that is bound if your water level is 0.75.

If you take some po4 out of the water, then the rock will release almost back up to where you were before. It is a task that you just have to keep doing.

It was likely the dry rock. Most sand from the ocean is not bound full of phosphate since the ocean has only a trace in the water. This is the hidden cost of dry/dead rock that the sellers do not tell you about... they have you worry about a mantis shrimp or aiptasia (which are easy to get rid of).

 

[Guiids]

You have to remove po4 from the water and the aragonie will unbind. It can take a long time. There is likely a massive amount of po4 that is bound if your water level is 0.75.

If you take some po4 out of the water, then the rock will release almost back up to where you were before. It is a task that you just have to keep doing.

It was likely the dry rock. Most sand from the ocean is not bound full of phosphate since the ocean has only a trace in the water. This is the hidden cost of dry/dead rock that the sellers do not tell you about... they have you worry about a mantis shrimp or aiptasia (which are easy to get rid of).

So just keep doing huge 50% water changes and waiting a few days in between?' Im reading some people have no issue with coral at 0.5 ppm phosphate? Very novice so I'll follow what y'all suggest. Luckily haven't bought coral yet.

 

[jda]

Water changes won't do much for po4 reduction. There is just so little in the water column compared to the rock. GFO, Lanthanum Chloride, Aluminum Oxide are better choices since they bind more from the water.

Water changes are awesome for other things, so I would still do them.

Some corals will not have any issues with 0.50 of po4. Some will suffer a bit and grow slow. Some will not do well at all and die. The whole problem with people who post that they have "X.XX of po4 and their corals are fine" is that it lacks nuance since there are differences that matter. You can seek out corals that are amenable to your desired po4 levels - it will be a subset, but there is some zen in this not having to work as hard or spend as much money on media.