phosphate going up after a refill in gfo reactor

[GSnake]

hello,
ive been testing weekly using hanna ULR for po4. the general trend has been po4 goes way down after a GFO refill (may21 @ 0.02) then slowly creeps up weekly 0.09>0.02>0.05>0.06. I did a half cup refill of HC GFO at this point again (brs recommended amount) waited a few days and tested 0.09, then tested again for 0.08 with the 2nd cuvette.

how has my phosphate not gone down after this refill? it was almost no effect. but i see it tumbling like normal. i did not change anything to my tank except do a fragging session this week to trim some coral.
is the GFO really shot? i refilled on 25th, and tested twice today on the 29th.

 

[GSnake]

i found an older thread, sorry,

BRS says GFO should be changed 4-8 weeks, i guess this only applies if your already around 0.03? or <0.1?

if the effluent is anything above 0.00, is it reasonable to change GFO after a week?
I dont want to waste any gfo but should a week be enough time for it to work, even at low levels?

 

[gbroadbridge]

hello,
ive been testing weekly using hanna ULR for po4. the general trend has been po4 goes way down after a GFO refill (may21 @ 0.02) then slowly creeps up weekly 0.09>0.02>0.05>0.06. I did a half cup refill of HC GFO at this point again (brs recommended amount) waited a few days and tested 0.09, then tested again for 0.08 with the 2nd cuvette.

how has my phosphate not gone down after this refill? it was almost no effect. but i see it tumbling like normal. i did not change anything to my tank except do a fragging session this week to trim some coral.
is the GFO really shot? i refilled on 25th, and tested twice today on the 29th.

Phosphate is leaching back out from Carbonate Rock and sand.

It actually can take a long time to remove the phosphate reservoir.

Simply keep changing the GFO once the phosphate rises, eventually the level will drop and stay down for weeks

 

[Dan_P]

hello,
ive been testing weekly using hanna ULR for po4. the general trend has been po4 goes way down after a GFO refill (may21 @ 0.02) then slowly creeps up weekly 0.09>0.02>0.05>0.06. I did a half cup refill of HC GFO at this point again (brs recommended amount) waited a few days and tested 0.09, then tested again for 0.08 with the 2nd cuvette.

how has my phosphate not gone down after this refill? it was almost no effect. but i see it tumbling like normal. i did not change anything to my tank except do a fragging session this week to trim some coral.
is the GFO really shot? i refilled on 25th, and tested twice today on the 29th.

What was the phosphate level just before changing the GFO?

 

[Randy Holmes-Farley Verified Community Expert]

A time based recommendation on when to replace GFO is no more useful than suggesting you get gas for your car every 6 days. The rate depends on the level of phosphate in the water, and how well you flow water through it.

 

[areefer01]

A time based recommendation on when to replace GFO is no more useful than suggesting you get gas for your car every 6 days. The rate depends on the level of phosphate in the water, and how well you flow water through it.

Good explanation.

I myself have been trying to get phosphates under control with little to no luck. As you pointed out flow through the GFO and how much it has removed since I replaced it the only way to tell is by running a test on it. I'm glad the Hanna kit is easy enough and quick to use but in my experience today replacement for me is anywhere between 4 days and 2 weeks tops.

GFO is cumbersome to use so can understand why LC is favored over it (in most cases). That bottle of SeaKlear on my workbench yells at me every time I pass it. Just need a low, and safe, dose to maybe try it out.

Hope your day, and weekend, is going well. Liked the gas analogy

 

[Treefer32]

Good explanation.

I myself have been trying to get phosphates under control with little to no luck. As you pointed out flow through the GFO and how much it has removed since I replaced it the only way to tell is by running a test on it. I'm glad the Hanna kit is easy enough and quick to use but in my experience today replacement for me is anywhere between 4 days and 2 weeks tops.

GFO is cumbersome to use so can understand why LC is favored over it (in most cases). That bottle of SeaKlear on my workbench yells at me every time I pass it. Just need a low, and safe, dose to maybe try it out.

Hope your day, and weekend, is going well. Liked the gas analogy

I struggle as well with a my 340 gallon display. I don't use GFO because it's costly and it's o.k. maybe for maintenance but on large tanks, the amount of phosphates absorbed by rock and released by rock is more than GFO could handle.

I use Lanthinum, but I don't like using it. I visibly see changes in my LPS corals after a month or two of dosing it. I've not determined whether it's due to the Lanthinum itself or the reduced phosphates over time. right now my phosphates remain stable around .35 ppm with no dosing and no water changes. I would prefer them under .2 as that's when my SPS really are colored up and looking good.

I think the LPS have grown used to higher phosphates and use it for food. Reduced amounts make them angry.