Why is my phosphate not dropping?

[Kan9]

Thanks in advance for those willing to assist. I have a 215 gallon aquarium I set up a little over a month ago, no fish or coral, just added about 5 Trochus snails and 3 small hermit crabs to address some of the algae I was seeing. For light I started running 2 lumenbars and 4 of the 8 T5s on the ATI about 2 weeks ago. Parameters are:

Temp 78
Salinity 1.026
Alk 10.1
Ammonia 0
Nitrates 0
Nitrites 0
PH 8
Magnesium 1350
and Phosphate .32

I have a refugium and some chaeto in there that seems to be doing fine in the week its been there.

I have about 75 lbs rock. I put in about 30% cured live rock from a sump , 35% dry rock that has been out of a reef aquarium for about 1 year and put in the aquarium about 3 weeks ago, and 35% previous dry rock that I cycled for almost 3 months. For the record, I suspect the dry rock I put in about 3 weeks ago is driving up phosphates for some reason...

So, any ideas why my phosphates would be so high with other parameters in line?

Thanks again in advance!

 

[W1ngz]

Phosphates can take a long time to drop using just a refugium. They're high most likely because it's a new tank, there's stuff on the rocks breaking down, and the biology that consumes them hasn't developed yet in a new tank.

A refugium is great for maintaining phos, but you might need something a little more aggressive (temporarily) to lower phosphates. It binds lightly to calcium carbonate and aragonite (basically all the rock and sand). It will drop with some GFO or similar in a reactor or a bag in the filter area, and the rocks will fill it up again until they start to get depleted, so initially you might not notice it come down much at all, then you'll get a slow steady decline.

Go easy on the media and test phosphate regularly so you don't hit bottom with them. From 0.32 I'd stop the GFO at 0.18-0.2 for a week, then continue down to 0.1, pause and then try and push it down to 0.05.

 

[YankeeTankee]

+1 on temporary passive GFO

Test often

 

[Kan9]

Phosphates can take a long time to drop using just a refugium. They're high most likely because it's a new tank, there's stuff on the rocks breaking down, and the biology that consumes them hasn't developed yet in a new tank.

A refugium is great for maintaining phos, but you might need something a little more aggressive (temporarily) to lower phosphates. It binds lightly to calcium carbonate and aragonite (basically all the rock and sand). It will drop with some GFO or similar in a reactor or a bag in the filter area, and the rocks will fill it up again until they start to get depleted, so initially you might not notice it come down much at all, then you'll get a slow steady decline.

Go easy on the media and test phosphate regularly so you don't hit bottom with them. From 0.32 I'd stop the GFO at 0.18-0.2 for a week, then continue down to 0.1, pause and then try and push it down to 0.05.

Great advise, thank you. I do have some GFO as well as some high capacity GFO. Do you think it will be OK to put 1&3/4 cup of high capacity GFO in a filter bag and put it in the sump? I did forget to add-I've been doing a 3 gallons/day water change.

 

[YankeeTankee]

Just dont forget to rinse the gfo

 

[stephj03]

Are you sure your nitrate is 0? What test kit are you using for this? A balanced tank typically has more nitrate than phosphate so if you really are bottomed out on that parameter it will be hard to bring phosphate down without a lot of water changes and constant GFO.

If there aren't any corals in the tank you could try to feed the fish heavy and see if that provides enough nitrate.

 

[W1ngz]

Great advise, thank you. I do have some GFO as well as some high capacity GFO. Do you think it will be OK to put 1&3/4 cup of high capacity GFO in a filter bag and put it in the sump? I did forget to add-I've been doing a 3 gallons/day water change.

I wouldn't just toss it randomly in the sump. Choose a high flow area where most or all of the water will pass through it. A reactor is most efficient. If you have multiple filter socks, you could put it in one of them.

 

[W1ngz]

Are you sure your nitrate is 0?

Nice catch, I missed that detail when I read the first post. Definitely more feeding, that will get the refugium to work a little harder.

 

[Kan9]

I have no fish. I am using a Bubble Magnus roller filter, so no filter sock. I have tested Nitrates a few times in the last 10 days or so-always showing 0 from what I can tell (API test kit). Should I still feed with only a small CUC in the tank and if so how much? Thanks!

 

[W1ngz]

With no fish or corals, just a few pieces of food for the critters will be fine. Dim the lights to the lowest setting to prevent algae from starting. Cut the light on the refugium to just a couple of hours to keep the chaeto alive. It's early for a refugium on that system, and that's where all your nitrates went I'd bet.

 

[Hemmdog]

API is not very accurate.
Grab salifert, Red Sea as a backup.

 

[Kan9]

With no fish or corals, just a few pieces of food for the critters will be fine. Dim the lights to the lowest setting to prevent algae from starting. Cut the light on the refugium to just a couple of hours to keep the chaeto alive. It's early for a refugium on that system, and that's where all your nitrates went I'd bet.

Perfect, will do!

 

[Kan9]

API is not very accurate.
Grab salifert, Red Sea as a backup.

Just bought one, thanks for the heads up!