High Phosphate, Low nitrate

[abbi_lester]

I need some help fixing my high phosphates. My tank has been running for about 6 months now and I have a pair of clown fish who seem to be very happy.I have a small refugium and skimmer that hang on the back of the tank to help with nutrient levels. I was looking to start adding some soft corals however based off of Salifert test kits Nitrates are sitting at about 2ppm and phosphates have always been very high of around 1.0ppm! (most people seem to say to aim for around 0.03ppm). I have yet to get any CUC but I'm assuming this won't really help my problem very much. Would adding coral help to use up the phosphate in the water?, How else could I lower my phosphates?

Thanks

 

[Timfish]

You didn't mention water changes but I would suggest around a third monthly (I like 5% to 10% weekly).

Over the decades I've seen a wide range of ratios in my systems. What I aim for is PO4 between .03 mg/l and .3 mg/l. For nitrate below 5 mg/l. GFO works well to remove excess PO4, wherevr you decide that number is for your system.

FWIW .03 mg/l is the threshold level to prevent phosphorus limitation in corals, identified by researchers at Southampton University in England using corals maintained in an aquarium for about a decade. .3 mg/l is what corals are subjected to with upwelling in the ocean. .5 mg/l is acceptable as acros have been shown to incease growth up to this level. .9mg/l is the level teh Steinhart Aqaurium's ex situ sexually reproduced acro colonies are being grwon out with. Rich Ross's (who's part of the team at Steinhart) has his acro dominate mixed reef sitting at 1.8 mg/l, his tank can be seen at the beginning of his MACNA presentation on phosphate.

I'm fine if I don't have any detectable nitrate. Corals have simbiotic cyanobacteria, diazotrophs, that can provide nitrates. Corals much prefer the dissolved organic forms of nitrogen in amino acids and urea and the dissolved inorganic ammonia.

Fig. 3 from this paper Context Dependant Effects of Nutrient Loading on the Coral-Algal Mutualism



And to add to the complexity of the picture, depending on how corals are feeding and the food webs in reef ecosystems, corals might be the source of PO4 (aka DIP, Dissolved Inorganic Phosphorus) in an aquarium.

 

[abbi_lester]

I forgot to add that I do a weekly water change of 10%. Thank you for your help

 

[Uncle99]

It’s a big number for phosphates.

If you’re absolutely confident in the test, then you can do two things to pull some out.

I’m not a fan of any of the phosphate tests except the Hanna UL phosphorus checker, the colour meter helps me be more consistent than my eye.

But go slow, you don’t want a quick drop especially if your running that level for some time.

If your 1ppm phosphate, GFO is very expensive so I might consider an LC treatment with something like Phosphate X and very tight sock until I reach .3ppm, then use GFO in some reactor or flow area to find a spot in the .1-.2ppm range and maintain that range, day in and day out.

Water change is not going to be effective in your case cause you have 2ppm nitrate and that’s fine, but we don’t want to lower that number.

 

[FUNGI]

Your softies are going to love those numbers.....IMO, I wouldn't change anything, if anything, increase your nitrates.....

 

[abbi_lester]

I currently don't have a filter sock or reactor I have just been using filter sponge as I have a small tank (35L) with no sump. I guess I could possibly get a tight filter sock to replace the filter sponge and LC treatment to try and lower the phosphates.
Would you suggest getting a small frag of coral possibly some zoanthids and see how it does?

 

[Reef Puncher]

i dont trust that phosphate number. 1.0? do yourself a favor and buy this. Dont buy the Ultra low range. its just more work where the low range will do just fine. its the ONLY phosphate tester i trust. even over salifert.

Phosphate Low Range Colorimeter HI713 Hanna Checker - Fresh & Marine Water

Why does BRS recommend this? The Hanna Phosphate Checker is an awesome little tool that will give you accurate easy to read results. If you have bad eyes or have a hard time with color change test kits, the digital readout on the Hanna checkers is super easy to read. The biggest key with Hanna...

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