GFO works and there is nothing innovative here, but perhaps this will be helpful to others. I previously struggled to get good results with GFO in small water volumes.
I keep a stable PO4 range around 0.08 ppm most of the time with carbon dosing (NP bacto), skimmer, and consistent food additions with an auto feeder. The balance took a while to find but it works well. My tank is only 100L. Occasionally when I get a new fish or get on a coral feeding kick, my phosphate jumps above my target range and doesn’t come back down so I take action to bring it back down with GFO. I’ve used the approach below many times and find it repeatable, so I thought I would share in case someone else finds it useful.
Here is my method to lower phosphates…
I add a small amount of GFO in a bag with carbon. For my 100L I use a tablespoon to start. I monitor daily or even 2x per day and then add another small bag of GFO when phosphate stops dropping. Rinse and repeat. I leave the original bag(s) in and just keep adding small bags (I don’t use a reactor).
In find that by adding small amounts I can keep a steady downward trend until I reach my target. Then I start removing the bags in reverse order every 2-3 days. This prevents the PO4 from changing quickly and prevents it from rising again after I reach my target. I figure that by going slowly I am removing larger amounts of total PO4 mass from tank, rather than smaller amounts from the water quickly which just get replenished through release from calcium carbonate surfaces.
The idea is that some of the PO4 is in the water and some (more?) is bound to the rocks and sand. By removing the PO4 slowly from the water, the corals don’t get stressed and PO4 is also slowly released from the calcium carbonate surfaces to get removed.
By removing one bag of GFO at a time, PO4 is still being removed, though more slowly by the bags that have older more saturated GFO. I usually only use 2 or 3 bags total, so it’s not complicated. After a couple days at the target PO4 I remove the last bag. The total process takes a week or two, but I don’t let phosphate get over about 0.25 ppm before I start the process. I keep the bags to use again in the future (in the same order).
I started this approach because I found GFO in larger amounts stripped the water too fast and PO4 would bottom out. The corals would react poorly. Then I would remove the GFO and PO4 would spike back up again. This YO-YO just stressed things out more. At one point I actually gave up GFO entirely for this little tank.
The unexpected effect was PO4 would stay in the target range after all the GFO was out and I was just back to carbon dosing.
Cheers
I keep a stable PO4 range around 0.08 ppm most of the time with carbon dosing (NP bacto), skimmer, and consistent food additions with an auto feeder. The balance took a while to find but it works well. My tank is only 100L. Occasionally when I get a new fish or get on a coral feeding kick, my phosphate jumps above my target range and doesn’t come back down so I take action to bring it back down with GFO. I’ve used the approach below many times and find it repeatable, so I thought I would share in case someone else finds it useful.
Here is my method to lower phosphates…
I add a small amount of GFO in a bag with carbon. For my 100L I use a tablespoon to start. I monitor daily or even 2x per day and then add another small bag of GFO when phosphate stops dropping. Rinse and repeat. I leave the original bag(s) in and just keep adding small bags (I don’t use a reactor).
In find that by adding small amounts I can keep a steady downward trend until I reach my target. Then I start removing the bags in reverse order every 2-3 days. This prevents the PO4 from changing quickly and prevents it from rising again after I reach my target. I figure that by going slowly I am removing larger amounts of total PO4 mass from tank, rather than smaller amounts from the water quickly which just get replenished through release from calcium carbonate surfaces.
The idea is that some of the PO4 is in the water and some (more?) is bound to the rocks and sand. By removing the PO4 slowly from the water, the corals don’t get stressed and PO4 is also slowly released from the calcium carbonate surfaces to get removed.
By removing one bag of GFO at a time, PO4 is still being removed, though more slowly by the bags that have older more saturated GFO. I usually only use 2 or 3 bags total, so it’s not complicated. After a couple days at the target PO4 I remove the last bag. The total process takes a week or two, but I don’t let phosphate get over about 0.25 ppm before I start the process. I keep the bags to use again in the future (in the same order).
I started this approach because I found GFO in larger amounts stripped the water too fast and PO4 would bottom out. The corals would react poorly. Then I would remove the GFO and PO4 would spike back up again. This YO-YO just stressed things out more. At one point I actually gave up GFO entirely for this little tank.
The unexpected effect was PO4 would stay in the target range after all the GFO was out and I was just back to carbon dosing.
Cheers
