Heavy GFO Usage

[jbilliel]

My tank has been up for about six months now and since day one the phosphates have been high. I am using RODI water which is consistently testing at 0 TDS. I have about 15 fish and a bunch of softies in a 90 gallon tank. I feed them one cube of mysis shrink in the evening and pellets in the morning so I don't think I am overfeeding.

To correct the Phosphates I have been running GFO in a reactor which gets them down to about .06, but I am having to change the GFO media often (like every 2-3 weeks). What else can introduce phosphates into the aquarium? I am stumped.... I also have a refugium which is working well and keeping the nitrates below 3ppm.

Any thoughts?

 

[andrewey]

What were your levels at previously and how recently has the phosphate been at .06? When phosphate levels are elevated, the phosphate will bind to your live rock or substrate. As the phosphate levels in the water decrease, as in the case of GFO use, the phosphate will release back into the water column, which could explain your findings.

The other consideration would be phosphate addition from any other additives (e.g. coral food).

Lastly, when you say you have to change the GFO media every 2-3 weeks, is that because the phosphate level is starting to rise? What is it rising to and what are you using to check your phosphate? What is your target phosphate level?

 

[jbilliel]

The phosphate prior to putting the reactor on was high, like in the .40+ ppm high. With 1.5 cups of GFO in the reactor it will drop down to about 0.03 ppm and then will slowly start increasing as it becomes exhausted. At 3 weeks the phosphate level is back up to 0.20 ppm

Edit - Here are the mysis shrimp that I feed the tank -> https://www.liveaquaria.com/product/3733/?pcatid=3733

 

[Nanojoe]

.06 is not a terrible number to be at honestly. As long you are not seeing increased algae growth... Be sure to rinse the mysis as well!

Adding another phosphate removal media could help too. Seachem phosguard or Continuum CaptivPhos - W are my personal go-to's.

 

[jbilliel]

.06 is not a terrible number to be at honestly. As long you are not seeing increased algae growth... Be sure to rinse the mysis as well!

Adding another phosphate removal media could help too. Seachem phosguard or Continuum CaptivPhos - W are my personal go-to's.

I just throw one cube into the feeder ring and let the water disolve it while the fish eat it like crazy. Is that a problem?

 

[Nanojoe]

I just throw one cube into the feeder ring and let the water disolve it while the fish eat it like crazy. Is that a problem?

Yes, the oils of the mysis shrimp and water they use to freeze the mysis together for packaging all contain nutrients / phosphates. Adding to your phosphate issue.. get a net and rinse them under some tap or RODI water if you have extra to do so.

 

[andrewey]

You can likely skip the rinsing step

Per Randy:

" So the hypothetical rinsing step has removed about 1 percent of the phosphate in that food. .....That amount washed away does not seem significant with respect to the "in tank" target level of about 50-100 times that level (say, 0.015 to 0.03 ppm), nor does it seem significant relative to the total amount of phosphate actually added each day in foods (which is perhaps 50-1000 times as much......Again, the conclusion I make is that rinsing is not really worthwhile, in my opinion."

 

[NashobaTek]

Lol, my phosphate was at 10+ , I started using phosguard and now it's at 1 and I can't seem to get it any lower. Everything seems to be doing well.

 

[Uncle99]

What test kit are you using?

 

[NashobaTek]

Me? API , I know they're not real accurate

 

[robbyg]

What were your levels at previously and how recently has the phosphate been at .06? When phosphate levels are elevated, the phosphate will bind to your live rock or substrate. As the phosphate levels in the water decrease, as in the case of GFO use, the phosphate will release back into the water column, which could explain your findings.

The other consideration would be phosphate addition from any other additives (e.g. coral food).

Lastly, when you say you have to change the GFO media every 2-3 weeks, is that because the phosphate level is starting to rise? What is it rising to and what are you using to check your phosphate? What is your target phosphate level?

That is a myth and I use to believe it when my 15 year old rock work had a massive GHA outbreak.
Long story short I disproved it and actually found what the real issue is.

 

[andrewkw]

What kind of GFO? if it's standard grade stuff it's supposed to be swapped out every couple of weeks. You want high capacity if you want it to last longer.

 

[andrewey]

That is a myth and I use to believe it when my 15 year old rock work had a massive GHA outbreak.
Long story short I disproved it and actually found what the real issue is.

May I ask why you say that's a myth? Do you mean the mechanism or only the application in this instance? If it's the mechanism, that might be something you might want to discuss with @Randy Holmes-Farley as he has written extensively about the role of these surfaces with regard to phosphate (e.g. http://reefkeeping.com/issues/2006-09/rhf/index.php).

 

[Uncle99]

Me? API , I know they're not real accurate

No, sorry, it was for the OP.

Using hobby grade tests, especially API, can lead us in the wrong direction.

It’s likely not even close.
Salifert is better............Hanna ULR best.............I use both of these with phosphate measuring because the amounts are so, so low..........I still have an API so here’s today’s numbers.
Hanna 0.022ppm (22 ppb)
Salifert 0.03 ppm (30 ppb)
API 0.25 ppm (250 ppb)

No sump, no refuge, just rock and skimmer.

Over the years I have learned to let the tank tell me where phosphate can run without resorting to number chasing.

My tank Phosphate has run anywhere from 0.03 -.20 for extended periods, No change in corals at all.
What they don’t like is change.

So, forget the API (it’s just not sensitive enough) stop GFO, and se3 where the number falls.

If you can get it in the 0.03-.2 range, I would trade stability for specific numbers anytime,

 

[joseserrano]

Feed less, change gfo more often. Phosphate can be coming from rocks

 

[jbilliel]

My numbers are from a Hanna ULR. I am using the standard grade GFO as BRS has been out of the better stuff for months now

 

[Randy Holmes-Farley]

2-3 weeks does not seem unusual for GFO depletion.

 

[jbilliel]

2-3 weeks does not seem unusual for GFO depletion.

I am glad to hear that Randy - I was referencing many of the manufacturers websites that are saying 2-3 months

 

[NashobaTek]

I am glad to hear that Randy - I was referencing many of the manufacturers websites that are saying 2-3 months

Phosguard says every 4 days until it's down where you want it.