Phosphates won't go down.

[shane.c02]

Aloha from Hawaii,

I am a student at a university in Hawaii. I was tasked with the project of maintaining a saltwater, reef aquarium in our science building. I was trained by the aquarist before me who has moved on. I am having a hard time bringing phosphates down. We had a disease outbreak a while ago, treated that, and after removing all the treatment the phosphates spiked so high it was unbelievable (10 ppm), then followed an insane hair algae bloomed. I tackled the algae and I lowered the phosphates to 2ppm, but they have stayed now at 1.5-2 ppm for a few months now. Water changes aren't affecting much and I've even been doing six phosguard absorbers for a couple days.

I have had zero fish and corals in the aquarium for months. It's empty besides live rock, a reticulated cowrie, and a common urchin, with trace amounts of copepods and amphipods. I don't add any nutrients and the only thing producing waste is the cowrie and urchin who I feed pieces of nori a couple times a week.

I do weekly 20% (60 gallons) water changes and vaccum the gravel to try to combat the high phosphates but its no use. I'm relatively new to saltwater aquariums but I know I can do it because there is a separate lab aquarium (150 gallons) that I have stabilized to perfection with zoas, nems, and fish. Something is just wrong with this aquarium that I'm stumped about.

It is 310 gallon aquarium including the tanks below with all the filtration (skimmer, filters, biofilters, return pumps).

Any advice would help. I attached a picture of the tank and parts below if that helps.

Shane

 

[Randy Holmes-Farley Verified Community Expert]

Water changes aren’t as effective at reducing phosphate as one might think because a lot of it reversible bonds to the surfaces of live rock and sand. It comes off as you try to lower the levels.

Lanthanum dosing is going to be the cheapest solution, but iron oxide (GFO), aluminum oxide (such as Phosguard) and soluble iron dosing all can work.

 

[Miami Reef]

Lanthanum chloride is fantastic for this purpose. It’s very inexpensive and it’s a beast for reducing high levels since you don’t need to change media.

GFO will be very expensive for your size tank and phosphate levels.

Lanthanum seems to cause issues with some tangs (very hit or miss.) Since your tank doesn’t have any, it’s fantastic.

I can’t think of a single reason why lanthanum wouldn’t be the best option in this scenario.

 

[shane.c02]

Lanthanum chloride is fantastic for this purpose. It’s very inexpensive and it’s a beast for reducing high levels since you don’t need to change media.

GFO will be very expensive for your size tank and phosphate levels.

Lanthanum seems to cause issues with some tangs (very hit or miss.) Since your tank doesn’t have any, it’s fantastic.

I can’t think of a single reason why lanthanum wouldn’t be the best option in this scenario.

This is great. Does Lanthanum stick around after I use it? Like… do I have to do heavy water changes to get rid of it before adding fish and corals? If yes, what % water change should I do?

 

[BryanM]

This is great. Does Lanthanum stick around after I use it? Like… do I have to do heavy water changes to get rid of it before adding fish and corals? If yes, what % water change should I do?

I dosed it in to a 1 micron filter sock in my sump. I was changing the sock once a month, and when I was done dosing I just removed it altogether.

 

[Randy Holmes-Farley Verified Community Expert]

This is great. Does Lanthanum stick around after I use it? Like… do I have to do heavy water changes to get rid of it before adding fish and corals? If yes, what % water change should I do?

It is often removed by catching solids on a filter sock, but not always, and I'm not sure in a fishless system it needs to be.

 

[Miami Reef]

This is great. Does Lanthanum stick around after I use it? Like… do I have to do heavy water changes to get rid of it before adding fish and corals? If yes, what % water change should I do?

It precipitates with phosphate and some carbonate. The free forms don’t really last very long, but a small portion will for a bit.

Theres no need to change water. The lanthanum phosphate can readily bind to organics which can become skimmed out (depending on the organic bound.)

I highly recommend it for your case. I like to think of it as sending little troops to attack an enemy lol.

 

[shane.c02]

It precipitates with phosphate and some carbonate. The free forms don’t really last very long, but a small portion will for a bit.

Theres no need to change water. The lanthanum phosphate can readily bind to organics which can become skimmed out (depending on the organic bound.)

I highly recommend it for your case. I like to think of it as sending little troops to attack an enemy lol.

This is great. Thank you so much!