Jestersix

Replacing GFO

Blaise006

Supporting Member
What is everyone’s routine to avoid the large impact it has on alkalinity?

Next time I replace Rowaphos I am going to attempt to cycle the reactor with my apex to turn it on for 10% of each hour and slowly work my way up.

I typically rinse my Rowaphos in RODI.

Rinsing and dropping it into the reactor at full speed typically results in a large alk dip for the next hour or two while I try to dose to counteract it. 1 ounce of Rowaphos has pushed my alk down roughly .3-.5 dkh following its addition. I assumed 1 ounce was a small starting dose on 60 gallons but I guess I was wrong.

Really interested to hear how everyone here manages their GFO/Rowa.


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JVU

BOD
Staff member
You’ve probably seen this already regarding why this is happening (there’s a whole section about this):


As far as how to deal with it, I don’t have any useful advice other than to only add small doses of GFO/Rowa at a time and supplement alk as needed. When I use GFO I usually mix it with carbon in a packed bed, so it’s much slower to react than tumbling in its own reactor. I don’t notice a change in alk, but I don’t use very much for my size tank.

In my opinion an occasional drop of 0.3-0.5 dKH that gets corrected isn’t too big of a deal. I think most tanks that dose alk continuously have similar swings every day due to increased usage during times of photosynthesis. If you know approximately how much your drop will be from experience you could just dose that amount of alk upfront when you drop in your new GFO.
 

ofzakaria

Supporting Member
What is everyone’s routine to avoid the large impact it has on alkalinity?

Next time I replace Rowaphos I am going to attempt to cycle the reactor with my apex to turn it on for 10% of each hour and slowly work my way up.

I typically rinse my Rowaphos in RODI.

Rinsing and dropping it into the reactor at full speed typically results in a large alk dip for the next hour or two while I try to dose to counteract it. 1 ounce of Rowaphos has pushed my alk down roughly .3-.5 dkh following its addition. I assumed 1 ounce was a small starting dose on 60 gallons but I guess I was wrong.

Really interested to hear how everyone here manages their GFO/Rowa.


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if the drop is high, it can indicate an overdosing so make sure you are following their instructions.


your drop is not that much, i usually just adjust my dosing a bit when i add Rowphos.

Careful Rowphos is very effective and fast working, i never have the reactor run full speed, usually slow speed.
 
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Blaise006

Supporting Member
if the drop is high, it can indicate an overdosing so make sure you are following their instructions.


your drop is not that much, i usually just adjust my dosing a bit when i add Rowphos.

Careful Rowphos is very effective and fast working, i never have the reactor run full speed, usually slow speed.

What would you say your turnover is on the reactor compared to the tank?

I have always been very cautious with GFO. I try to not use it if I don’t have to and I never add more than an ounce at any single time.

I was curious if anyone had ever recirculated some fresh seawater to run the reactor for an hour just to dilute the alkalinity impact. I am not sure if that would hamper the effectiveness of it though.

My thought process is that the carbonate would be pulled out and bind to the free sites over an hour and reduce the alk drop. I agree that my drop isn’t terrible but always looking to improve the process of I can :)

A concern I have about recirculating fresh saltwater is that it may cause carbonate to unbind in the display tank. I am not an expert at surface chemistry so I am not clear if GFO causes carbonate to precipitate out of the solution or just causes a drop in alkalinity through binding the various ions at the surface.


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Blaise006

Supporting Member
You’ve probably seen this already regarding why this is happening (there’s a whole section about this):


As far as how to deal with it, I don’t have any useful advice other than to only add small doses of GFO/Rowa at a time and supplement alk as needed. When I use GFO I usually mix it with carbon in a packed bed, so it’s much slower to react than tumbling in its own reactor. I don’t notice a change in alk, but I don’t use very much for my size tank.

In my opinion an occasional drop of 0.3-0.5 dKH that gets corrected isn’t too big of a deal. I think most tanks that dose alk continuously have similar swings every day due to increased usage during times of photosynthesis. If you know approximately how much your drop will be from experience you could just dose that amount of alk upfront when you drop in your new GFO.

Thanks for the article.

I am worried about doing those .3-.5 drops back to back within 24 hours. Essentially, I add an ounce of Rowaphos today and then another ounce tomorrow.

Is that too quick? I haven’t seen any adverse effect on my sps but just want to be cautious.


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Blaise006

Supporting Member
I also think the cycling of the reactor would be a great way to handle it but I am concerned about hydrogen sulfide forming in a closed reactor.


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ofzakaria

Supporting Member
Thanks for the article.

I am worried about doing those .3-.5 drops back to back within 24 hours. Essentially, I add an ounce of Rowaphos today and then another ounce tomorrow.

Is that too quick? I haven’t seen any adverse effect on my sps but just want to be cautious.


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Sorry I forgot not understanding what you mean exactly.
The drop in alk, usually happens one time, it will not continue to drop. So you can simply adjust your dosing to compensate for the drop.
Sorry if I miss understood your question.
 

Blaise006

Supporting Member
Sorry I forgot not understanding what you mean exactly.
The drop in alk, usually happens one time, it will not continue to drop. So you can simply adjust your dosing to compensate for the drop.
Sorry if I miss understood your question.

No worries, agreed on that point that it’s a one time occurrence. My concern is having to do that “one” time occurrence back to back.

Example: Say I need 2 ounces based on the Rowaphos calculator. I only ever dose a max of 1 ounce at any single point in time given the alk drop. So normally I spread that out over two days. 1 ounce today and 1 ounce tomorrow. I dose to bring alk back up but I am concerned about two points.

A: Multiple doses creates instability on the short term of high fluctuations. It is hard to say the drops in alkalinity aren’t larger. These are just the testing points I happen to capture via the trident.

B: Given that short term instability, I wonder if there is a way to dampen the alkalinity impact via recirculating the GFO reactor with fresh saltwater for a couple hours so that carbonate binds up the free sites (but that could release the carbonate in my DT, then put the reactor on my system, I don’t know since I am not really an expert on that), or it dampens the effect of Rowaphos to strip phosphate.

B1: Cycling the reactor sounds good on paper to me as it will spread the impact to alkalinity over a longer period of time creating a less steep drop, but I worry about the formation of hydrogen sulfide in stagnant water.

So I was curious what everyone dose and it sounds like they dose to correct it.


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ofzakaria

Supporting Member
No worries, agreed on that point that it’s a one time occurrence. My concern is having to do that “one” time occurrence back to back.

Example: Say I need 2 ounces based on the Rowaphos calculator. I only ever dose a max of 1 ounce at any single point in time given the alk drop. So normally I spread that out over two days. 1 ounce today and 1 ounce tomorrow. I dose to bring alk back up but I am concerned about two points.

A: Multiple doses creates instability on the short term of high fluctuations. It is hard to say the drops in alkalinity aren’t larger. These are just the testing points I happen to capture via the trident.

B: Given that short term instability, I wonder if there is a way to dampen the alkalinity impact via recirculating the GFO reactor with fresh saltwater for a couple hours so that carbonate binds up the free sites (but that could release the carbonate in my DT, then put the reactor on my system, I don’t know since I am not really an expert on that), or it dampens the effect of Rowaphos to strip phosphate.

B1: Cycling the reactor sounds good on paper to me as it will spread the impact to alkalinity over a longer period of time creating a less steep drop, but I worry about the formation of hydrogen sulfide in stagnant water.

So I was curious what everyone dose and it sounds like they dose to correct it.


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Aha got it.
Yeh what I do is dose the rowphos that I need, adjust alk drop (I have khg so I can tell the drop immediately) and thats it..
 

Coral reefer

BOD
Staff member
I do nothing and don’t worry about this lol. I’m sure you have a point, but I also feel you’re over thinking it a little. Is it possible to find a best way with the least impacts on alk? Probably. Keep experimenting and see what you find.
 

max_nano

Supporting Member
Do you use a salt that has a higher alk than you normally keep? You could put in new rowaphos while doing a water change with higher alk salt and they may balance out.

Or replace it and dose 5mL of 2 part in addition to your scheduled dose as a buffer and see if it removed the dip. Then adjust when adding the next time. If you add the same amount of rowaphos it would bind the same amount of carbonate so there is a balance to be found?

Just some ideas I’m having, I don’t have personal experience with rowaphos
 

Blaise006

Supporting Member
I do nothing and don’t worry about this lol. I’m sure you have a point, but I also feel you’re over thinking it a little. Is it possible to find a best way with the least impacts on alk? Probably. Keep experimenting and see what you find.

Thanks, I do tend to overthink. So ya got me there haha :)


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The_Lazy_Reefer

BOD
Staff member
Well since setting up my KH director I got to watch this change in real time. For my 75 gallons of water I run 1 cup carbon and 1/2 cup of gfo mixed in 1 reactor and this resulted in a .5 dkh drop. Now when changing out gfo I know to add some 2 part to make up for that loss. Never noticed an issue before but now that I know it’s nice to keep it stable.
 

Gablami

Supporting Member
What is everyone’s routine to avoid the large impact it has on alkalinity?

Next time I replace Rowaphos I am going to attempt to cycle the reactor with my apex to turn it on for 10% of each hour and slowly work my way up.

I typically rinse my Rowaphos in RODI.

Rinsing and dropping it into the reactor at full speed typically results in a large alk dip for the next hour or two while I try to dose to counteract it. 1 ounce of Rowaphos has pushed my alk down roughly .3-.5 dkh following its addition. I assumed 1 ounce was a small starting dose on 60 gallons but I guess I was wrong.

Really interested to hear how everyone here manages their GFO/Rowa.


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Check out the avast marine spyglass reactor. I have a mini. Love it for GFO. Best thing about it is it doesn’t clog over time, so you don’t need to continually adjust the inflow to keep it tumbling. Second best thing about it is you don’t have to take down the whole assembly to add more GFO. If my phosphate is rising, I’ll rinse a few tablespoons of gfo in rodi, and use a spoon to drop it into the reactor while it’s running. I can add small amounts as often as I want, which has a much smaller impact on alkalinity than changing out all the media at one time.



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Rostato

Supporting Member
I have never even heard of this issue, and never noticed it. I “dose” a crap ton of Rowaphos every two weeks to my tank (8tbs for about 110 gallons). I guess I’ll have to pay more attention.

I also can’t see it making a huge difference. Even with constant dosing from my carx, and kalk reactor I still have about a .4 dkh swing throughout the day according to my kh guardian.
 

rygh

BOD
Staff member
Run less GFO, but change it more often!

A given mass of GFO will absorb a given mass of Phosphate.
So 4 cups every month is technically the same as 1 cup every week, as far as phosphate.

But key is the surge.
If your 4 cups depletes in 3 weeks, when you add it, you have a huge surge in adsorbtion, both phosphate and Alk as a side issue.
But when you do only 1 cup every week, that surge is much smaller (1/4 the size).

Bonus: You have far less issue with clogging, since detritus does not accumulate over a month.

+1 on spyglass media reactor. I use that when I run GFO. Works great.
 
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