Does GFO lower Alk and cause my SPS to RTN/STN?

[allabarton]

7-8 weeks ago I started having problems in my SPS tank. Corals were getting pale and/or brown, RTN/STN, no or minimal PE.

I did a few changes. One of them was taking GFO reactor off line. Corals started healing rapidly. SPS with STN got their PE and were on the way to recovery. Other colors started to get their colors and PE back.
My parameters've been stable.
Alk 149ppm/8.3dKH (Hanna)
Alk 8.4dKH/150ppm (Red Sea)
Ca 476 ppm (Hanna)
Ca 460 ppm (Red Sea)
Mg 1360 ppm (Red Sea New)
Mg 1320 ppm (Red Sea Old)
Salinity ~1.026
Nitrate 0.00 (Red Sea)
Phosphate 0.00-0.02 ppm (Hanna)
Ph 8.2-8.4

I decided to run GFO when needed. Since phosphate started slightly to go up I turned the reactor on for a few hours. Next day my corals did not look happy. SPS with STN started to pill their tissue again. Other ones started to loose their colors. Alk was still the same. And next day Alk dropped to 135ppm/7.56dKH and Ph 8.1.

My questions are:

Does GFO lower Alk and Ph? Could GFO cause SPS to STN and loose PE and color? Why and how?

I dose Kalkwasser via ATO with an Oprical Level Probe that run by GHL Profilux controller.

Thank you. Any input would be appreciated.

 

[ReddyW]

I'm sure someone knows more about this than me, but IME, too much GFO, especially high capacity GFO causes tissue recession on my LPS. Try using less or cutting flow to your reactor until you find a balance between phosphates and tissue recession.

 

[Skynyrd Fish]

Sps need a little phosphate. Cut back the gfo. I'm sure others will know more and chime in. Good luck and keep us posted.

 

[nozleman]

The same thing happened to my tank. I had phosphate so I put reactor online, all my sps stn and were gone this has happened twice to me. I dont know why or how but I think it was the cause! Sound like you had the same thing happen, maybe one of the pros can chime in with why this happens.

 

[bertoni]

In some tanks, GFO causes calcium carbonate precipitation, which will affect alkalinity (and the calcium level). Does the media look white? Calcium carbonate will look like a white coating or white areas on the GFO.

I'd be careful to rinse the GFO well. What brand are you using?

GFO seems to cause problems in some cases, likely by consuming too much of the phosphorus in the system. I'd run only small quantities in the system for a while, if any at all.

 

[ampemployee1]

My understanding is GFO will deplete alk somewhat. IME, SPS are very sensitive to rapid changes to any of the key params (alk/p/n/temp/etc). Consider keeping the reactor online, but running a smaller amount of GFO. There are online calculators for the recommended amounts based on system size and desired phosphate ranges. Cut the recommended amount in half as a starting point. That will keep the phosphate levels from moving too quickly in one direction or the other, and will also allow your ATO/Kalk to keep pace with the alk depletion and maintain the pH levels as well.

 

[tmz]

GFO will reduce PO4 which may lead to clearer water (less phytoplankton) and more intense light.
Lower PO4 may also increase increasing calcification by corals and other organisms which can use more alkalinity and calcium as a result .
Some precipitation may occur on the gfo itself.
PO4 itself is alkalinity, though a very small percentage of total alkalinity.

Some corals need a little time to adjust to drops in PO4 levels particularly when they are taken to very low levels. So PO4 reduction particularly in the low ranges below .05/.06ppm should be done incrementally.imo. Some lps come from water with significantly higher levels of PO4 but upper reef waters where sps dominate run around .005ppm PO4 and 0.2ppm NO3. However,the supply is the supply is consistent.
Fines may also irritate corals.
FWIW, corals in my sps, lps leathers etc in my system seem to do best with PO4 around .02 to .03 and NO3 around 0.2ppm .

 

[cnguyenl]

I noticed the same thing the last couple weeks. No polyp extension at all on my sps, and my lps don't open as much. Just cut back on my GFO. Will see if they improve.

 

[reefgeezer]

I have absolutely no evidence to support my actions but I always start the flow through new GFO at a very low level for about two days then increase it over the next three. I think this decreases the chance of causing any shock or other bad reactions I don't understand.

 

[coralreefdoc]

Too much flow thru the reactor, not necessarily coupled with too much GFO media, will rapidly deplete KH values, in addition to the other values/parameters i.e. Si02, PO4, etc.

I've been stating/warning about this phenomena around here, as well as other informative avenues, for some time now ...

 

[tmz]

Essentialy, less flow means less exposure to the surfaces on the gfo,ie less adsorbtion of PO4, et al and less grinding and fines.
However, lower flow could contribute to precipitation on the gfo . Slow tumble at the surface of the gfo in a reactor with a pelletized or sturdier gfo is my preference. I like the HC gfo from Bulk Reef supply for low dust and strudiness.

 

[Michigan Mike]

What kind of GFO are you using?
I've started using the BRS (standard grain GFO?) ...not the fine stuff that is more efficient.
I've noticed my ALK has been noticeably lower and have had to compensate for it more than normal.

 

[coralreefdoc]

There's no deficiency of GFO brand preference threads, but to directly answer your question ...

RowaPhos. There's no comparison, in my opinion/experience, especially if the price/cost variable/aspect isn't a determining factor

 

[allabarton]

Thank you for all your responses. I really appreciate it.

I use BRS HC GFO. I've used since the beginning. The last dose was 1.5 cup for about 190-200 g system.

I got some GHA on my rock that I was trying to get rid of. I must've put too much media. Plus dramatically cut back on feedings. I think the combination of these factors upset my corals.

What would be the best approach if my Phosphate is 0-0.03 and Nitrate stay at 0 (Hanna and Red Sea) but I still have GHA? I have only 7 3-5" fish in my180 g that I feed once a day frozen food and Nori/Pellets a few times a week. I just started giving Oyster Feast to my corals and dosing Red Sea Amino Acids. Do 10% weekly WC.
I am a little scarried to use GFO. Especially after I saw pictures of one experiment on 3Reef showing torch LPS would open as good as in tank with Vodka dosing and one with Biopellets. Thank you.

 

[keithhays]

Thank you for all your responses. I really appreciate it.

I use BRS HC GFO. I've used since the beginning. The last dose was 1.5 cup for about 190-200 g system.

I got some GHA on my rock that I was trying to get rid of. I must've put too much media. Plus dramatically cut back on feedings. I think the combination of these factors upset my corals.

What would be the best approach if my Phosphate is 0-0.03 and Nitrate stay at 0 (Hanna and Red Sea) but I still have GHA? I have only 7 3-5" fish in my180 g that I feed once a day frozen food and Nori/Pellets a few times a week. I just started giving Oyster Feast to my corals and dosing Red Sea Amino Acids. Do 10% weekly WC.
I am a little scarried to use GFO. Especially after I saw pictures of one experiment on 3Reef showing torch LPS would open as good as in tank with Vodka dosing and one with Biopellets. Thank you.

I use about the same amount of standard GFO on a 300 gallon system to which I dump a lot more food into and Phosphate doesn't register on the hanna (ppm). Since it is very likely with the GFO use your Phosphate is zero or nearly zero and since GFO does nothing for nitrate, you will need:

• Additional water changes (doesn't help a lot)
• Additional low oxygen filtering mechanisms i.e. Live rock, Seachem Matrix, autotrophic (sulfur) or heterotrophic (carbon fed) filters.
• Carbon dosing directly into the tank can be accomplished easily enough. This is essentially feeding the current low oxygen filtering mechanisms in your system so that they can multiply and strip more nitrate from your system. This method feeds all bacteria equally so make sure your skimmer is very efficient.

 

[keithhays]

...btw, your nitrate is likely not zero until after the algae have stripped it out. If you suddenly had no algae it would likely go way up.

 

[bertoni]

That phosphate range might be safe enough, although the precision of hobbyist equipment at low levels is limited. I might try backing off on the GFO a bit, if the corals are having troubles, and see how that goes. The problem might get better or worse, but the change should be safe enough if it's done gradually and reverse course if the situation gets worse.

 

[dg3147]

Did decreasing the GFO ever help?

 

[tmz]

Too much flow thru the reactor, not necessarily coupled with too much GFO media, will rapidly deplete KH values, in addition to the other values/parameters i.e. Si02, PO4, etc.

I've been stating/warning about this phenomena around here, as well as other informative avenues, for some time now ...

How do you think it will do that? I don't think it does reduce carbonate alkalinity other than if a lot of precipitation occurs on the media which would have little to nothing to do with flow ,ime tending toward more of that if anything at lesser flow,ime.
Ddh drops are likely to be insignificant from the gfo itself. The enhanced bio activity and consumption of alk and calcium resulting from cleaner water, more light and less PO4 are the major players ,imo and ime.

BTW, PO4 is alkainity,we just don't want very much of it as part of the total alkalinity.

What other informative avenues related to GFO are you talking about?

 

[_shorty_]

hmm - this brings up several points for me to monitor the next couple weeks as I move forward with installing my own GFO reactor tonight. Makes me a little nervous, actually...

I wonder if the Redfield ratio would be bennificial in Ops situation - raising NO3to reach that 16:1 - N ratio. I've read that it may help reduce cyano - will it reduce algae as well...? That was a total regurgitation, but something I've considered trying to achieve in my system eventually.