Effect of GFO on alk

[Melinda01]

I have been having issues with very high PO4 for a while now. A Clear water scrubber was inatalled in November to try to combat this. However, today during my parameter check my PO4 is still 0.88 via Hanna ULR . (Prior to the ATS the PO4 was over 1). The nitrates are 20. I do not feel that I overfeed, the tank isn’t overstocked, and the source RO/DI water reads 0.05. Looks like gfo and a reactor is the only option I have left. So I ordered a single reactor, HC GFO, and large particle AC today.
My alk is reading 7.4 via salifert. I just want to make sure that I will not drop it anymore when I start using the gfo. I currently do not dose alk. Thanks in advance for the responses.

 

[pdxmonkeyboy]

it should not affect your alk is the short answer. is this a newer tank? if so I would suspect that you have decaying organisms that are leaving phosphates into your tank. I think it would be highly unusual to have that high of phos in a mature tank unless you are not doing any water changes.

lastly, but a lot of gfo, it will likely get exhausted pretty quickly with those levels.

good luck!

 

[Melinda01]

it should not affect your alk is the short answer. is this a newer tank? if so I would suspect that you have decaying organisms that are leaving phosphates into your tank. I think it would be highly unusual to have that high of phos in a mature tank unless you are not doing any water changes.

lastly, but a lot of gfo, it will likely get exhausted pretty quickly with those levels.

good luck!

It has been up and running since 2013. I moved the tank in 2016 and have had issues since then. The nitrates were off the charts and I started vinegar dosing to bring them down. It worked and I have since stopped dosing, but I’m still fighting PO4. The company that moved the tank for me did not advise me to replace the sand and I’m guessing that has a lot to do with my problem. I have been doing massive (about 25% weekly) water changes for months with no effect on the PO4

 

[capt.dave]

Do you vacuum the sand when you do your water changes? Might help by pulling junk out.

I assume you're battling a massive algae issue with that much PO4. Manual removal is critical otherwise the PO4 just gets released again as the algae dies.

Do you have a cheato fuge? Those really help with a good grow light. Don't expect cheato in your fuge under a cheap CFL light to out compete GHA under high end lights in your display tank.

GFO works. Do that, too.

 

[Melinda01]

Do you vacuum the sand when you do your water changes? Might help by pulling junk out.

I assume you're battling a massive algae issue with that much PO4. Manual removal is critical otherwise the PO4 just gets released again as the algae dies.

Do you have a cheato fuge? Those really help with a good grow light. Don't expect cheato in your fuge under a cheap CFL light to out compete GHA under high end lights in your display tank.

GFO works. Do that, too.

Honestly the algae isn’t as bad as you would think. The sandbed turns green if I don’t blow it off every couple days and I only clean the glass every couple days as well. More than I would like, but considering the PO4 it could be much worse. There is some green algae on the rocks but it isn’t hair algae. Believe it or not the zoas, plate coral, and even the montis are actually doing pretty well growing and encrusting. In the pics the sunset monti has some algae on it. That is actually gone now and it has encrusted a lot more. These pics were taken a couple months ago. I would take pics now but the lights have gone down for the night. Apparently they have gotten used to the high PO4. I do blow off the sandbed and siphon it out with water changes. I don’t have a fuge. Wish I did!

 

[Randy Holmes-Farley Verified Community Expert]

I agree that the GFO won't cause a big drop, but it might accelerate precipitation of CaCO3 on or downstream of the GFO, and may even accelerate skeleton formation by corals as phosphate drops. So you will want to monitor alk.

 

[Melinda01]

I agree that the GFO won't cause a big drop, but it might accelerate precipitation of CaCO3 on or downstream of the GFO, and may even accelerate skeleton formation by corals as phosphate drops. So you will want to monitor alk.

Okay. Thanks for the reply. I’ll keep a close eye on the alk, calcium, mag, PO4. I usually test all parameters monthly but will test those weekly once the reactor is installed. I plan to underdose the GFO at 1st and bring down the PO4 slowly because I don’t want to throw the tank into shock.

 

[CindyKz]

Definitely go slow with the GFO, especially since everything is doing ok and you don't really have an algae problem. Whenever I go overboard with the GFO I end up with a cyano outbreak.

Good luck.

 

[Melinda01]

Definitely go slow with the GFO, especially since everything is doing ok and you don't really have an algae problem. Whenever I go overboard with the GFO I end up with a cyano outbreak.

Good luck.

Good to know. I already have some Cyano so I don’t want to make it worse. If I can dial it in to bring it down by 0.1 a week I’ll be happy. At that rate it’ll take two months to bring it down to acceptable levels but as you said, I really don’t have much of a problem right now. I still have a couple fish that I’d like to add in the meantime. Once they are through QT and ready to go I can start QT corals. Just don’t want to add any more corals until the parameters are dialed in. I did have a birdsnest that didn’t make it due to algae several months ago and would like to add another.
Here is a pic on the monti now. I looked at the date of the last pic that I posted and it was only a month ago. It is growing fast despite the PO4