Vodka dosing maxed out...best way to run GFO?

[boobookitty]

After 6+ months the vodka dosing has finally kicked in; nitrates are nicely low after hitting 50-100 at one point. I had a couple other threads on the long journey that took to get to this point.

Unfortunately, as is common, I'm left with excess phosphates; vodka dosing took phosphates down to around 0.75-1.0 and won't get them any lower. So I'm going to augment with GFO.

I've read a bunch of threads, but being new to GFO's despite running large tanks for 20 years, I was hoping for direction on actually using it. Specifically:

- Reactor or just media bag in a high flow area of the sump?

- Are there guidelines on how much GFO to use?

- If a reactor is the way to go, are there guidelines on what the water flow should be through it?

 

[mcgyvr]

Reactor is better as water is being forced through/around it in a somewhat controlled manner..
How much depends on tank size/phosphate amount.. Typically the manufacturers will have a chart or information for that specific product..
The flow should be slow enough so you aren't tumbling or pulverizing the GFO..
I'd suspect you can easily find videos online showing optimal flow based on looking at the reactor

 

[bertoni]

A reverse-flow filter, like the phosphate reactors, is the most efficient way to use the media if you are willing to tune the flow. The fluidization effect will increase the percentage of media that comes in contact with the water. The flow needs to be slow enough that the media isn't ground into powder.

Otherwise, a normal-flow reactor is good. I don't know that a bag in the sump would get enough flow forced through it, but it might work.

 

[homer1475]

Your more then likely nitrate limited now(0 nitrates but still high phosphates). This is what typically happens when carbon dosing, and requires the addition of nitrate to further reduce phosphates.



Once you add in some nitrates(look into potassium nitrate dosing. FW planted guys have been doing it for years) the bacteria kick up again further reducing phosphates.

 

[Uncle99]

I believe ROWAPHOS prefers users to run their specific (and IMO very effective) product in the filter bag (which is included), sandwiched between two filter media like sponge and carbon, or just in the sump. If you go with reactor, very gentle tumble, otherwise the effectiveness is quite lessened.

Your carbon dosing results are quite normal, make sure you don't bottom out your nitrate, 5-10ppm is fine.

 

[boobookitty]

I actually got the BRS reactor and media. Works really well; even with just a cup of media phosphates dropped 0.3 overnight.

 

[boobookitty]

Update and a weird issue: I installed the BRS reactor, using their heavy duty media, and it worked. Sort of. I’m using a cup at a time because I didn’t want to drastically drop phosphates, and that worked. First day it dropped from 1.1 to 0.8, at which point the media was exhausted since it plateaud. So another cup later, and it dropped to 0.5.

But it’s been stuck there. A new cup of media didn’t drop it at all, so I figured something went wrong and tried another cup, but phosphate has been stuck at 0.5 for days now. Same flow rate, same conditions (top of the media undulates so the water flow is right). No idea why phosphates won’t go lower.

Thoughts?

 

[Daddi0]

Perhaps leaching from the rock work?
Cheers! Mark

 

[Vinny Kreyling]

To check if media is exhausted check the water coming out of the reactor compared to tank water. The same or close & it's time to change media.

 

[boobookitty]

No, this is with brand new media...first couple of batches brought phosphates down 0.3 each day. The last two batches haven’t brought phosphates down at all.

I thought about leaching, but wouldn’t that have kept the levels elevated even for the first couple batches? Also vodka dosing brought them down as well, over months, so I had thought the leaching was done.

 

[Dan_P]

No, this is with brand new media...first couple of batches brought phosphates down 0.3 each day. The last two batches haven't brought phosphates down at all.

I thought about leaching, but wouldn't that have kept the levels elevated even for the first couple batches? Also vodka dosing brought them down as well, over months, so I had thought the leaching was done.

Do check the output of the reactor as suggested. We need to establish whether media is exhausted or not. If it is not exhausted and your system is stuck then maybe PO4 is being produced as fast as it is being adsorbed. If the media is exhausted, that explains the pause in removal. As someone suggested, once your system's PO4 level reaches a lower level, bound PO4 can start desorbing from the aragonite (rocks, sand) more readily. Need to know about the condition of the media to Sherlock Holmes this situation.

 

[boobookitty]

Ok, I installed a t so I can take readings on the output. This morning (11 hours ago) tank phosphate was still 0.51, hadn’t budged in a few days. This afternoon it’s actually 0.39, with the reactor output at 0.21, so apparently it’s starting to go down again and the media isn’t exhausted.

 

[boobookitty]

Update: this morning phosphate is back to 0.46, with reactor output still at 0.21. Very odd. I suppose leaching is going on.

 

[Vinny Kreyling]

Sounds like it, be prepared this could take a while.

 

[reefgeezer]

Carbon dosing while adding nitrate could help, but regenerating the GFO might be a better use of your resources. You're gonna need a lot for quite a while if all that rock is leaching phosphates.

 

[bertoni]

Leaching is very common. That range between the reactor and the tank seems rather wide, though. I'm not sure what's happening, but I'd just stay the course for the time being.

 

[boobookitty]

Update: tank phosphate has been stuck at a steady 0.43 for 4-5 days now. Reactor output ranges from 0.20 to 0.27, until it’s exhausted, which generally takes a couple days. Even while running with an exhausted reactor tank phosphate stays at 0.43, so that seems to be the cosmic background radiation level now for tank phosphate. I’m only using a cup or so of the high-density BRS GFO at a time to avoid drastic changes. Vodka dosing is keeping nitrates at 1 or less. So, riding out the phosphate leaching...

 

[bertoni]

That leaching could continue for quite a while. You can consider other approaches if the cost gets to be a bit much.

I'm not sure why it's taking so long for the media to be exhausted, but maybe the flow is a bit low. Of course, it's best not to abrade the media.

 

[boobookitty]

Yah, I’m moderating the flow to avoid abrasion. I can be patient, and I have a lot of media. Monitoring the reactor output every day for exhaustion/replacement.

I figured it’ll take a while for leaching. I’m wondering if, after it’s done, the vodka dosing will then be enough to take care of any phosphate issues as it keeps nitrate levels low.

 

[bertoni]

Patience is a good thing here.

I have no idea whether the vodka will keep the phosphate level down. Every tank is different.