Bio-Pellets and GFO

[slapshot]

I am running brs biopellets in a RO reactor and at the advise of others have stopped using gfo about two weeks before the addition of biopellets. The biopellets have been in action for about 7-8 weeks no noticable improvements in either nitrate or P04. 15-20 on nitrate .35 on P04. I feed pretty heavy have an auto feeder drop a small portion of spectrum pellets two times a day and feed arctipods or a frozen food when I get home 6 nights a week. 3 times a week I feed the corals some oyster feast.

In the beginning of the pellet revolution it was thought that in order to bring down both nitrates and phosphates, you needed to remove the GFO. This allowed the pellets to be colonized by bacteria that consume phosphates, or so was the theory. We have now come to realize that the two are linked in our systems. If you are adding phosphates at a rate greater than the pellets can remove, while they are removing nitrates, then the system stalls at some balance that is higher than we would like. It basically maintains the balance at the phosphate level of input.

I'm not sure scientifically what is going on, but to make a long story short go back to using GFO temporally and your nitrates will again start falling. Once your phosphates are down, the nitrate will come down and a new lower equalibrium will set in. The long term problem seems to be keeping the phosphates down so it doesn't creep up again. I am back to running GFO 1/2 of the time. Basically, two to three weeks in, two to three weeks out. This gives me time to run carbon in between.

[Flynnstone]

i have heard that you only add the GFO back into the system once the nitrates are down to zero and the phos is still present. trying to reach equalribrium is a topic of debate right now. some will say that the PO4 will leach back into the system from the rock where it has been bound with calcium, lanthanum ect. but can it actually leach back into the system at a ph that we keep our water, or does it require the ph to drop below 7.5 to leach back? basically if it were to leach into the water column itself to reach equallibrium, then would not the calcium be leaching also, and our rock would be breaking down?

[slapshot]

i have heard that you only add the GFO back into the system once the nitrates are down to zero and the phos is still present. trying to reach equalribrium is a topic of debate right now. some will say that the PO4 will leach back into the system from the rock where it has been bound with calcium, lanthanum ect. but can it actually leach back into the system at a ph that we keep our water, or does it require the ph to drop below 7.5 to leach back? basically if it were to leach into the water column itself to reach equallibrium, then would not the calcium be leaching also, and our rock would be breaking down?

I don't know how it all works but, I can tell you my system's nitrate settled at <2 intially then creeped back to 10. I added more pellets and it stayed between 10 and 20. It would not change. I added GFO and within two weeks the nitrates dropped to 5 while my phosphates went from 1 to .5.