ORP and Bacteria

[Randy Holmes-Farley]

Thanks for the update.

How fast is the flow through the biopellet reactor?

 

[eagle]

I started with 50 gph when first adding biopellets. As nutrients fell and ORP fell to the 420 range I slowed it down to 30 gph. My orp immediately responded by climbing higher over the next 2 days up into the 460 range. So the correlation is there, now I will continue to watch the relationship with nitrate levels.

 

[Randy Holmes-Farley]

Can you measure the ORP from the biopellet effluent before it gets to the skimmer?

 

[eagle]

That's a good idea. I will when I get home and let you know. I set it up with a bypass so I can measure the rate easily without unhooking from the skimmer. I should have thought about measuring that

 

[Randy Holmes-Farley]

Great, looking forward to it!

I've not seen anyone measure that before.

 

[eagle]

I think separating the skimmer is the best idea I ever had lol. I had many skimmers. Recirculating and in sump. It's always been a pain to know if I'm running too much flow through my sump or too much flow through the skimmer etc. Too many variables. My skimmer now is an in sump but the compartment is separate from the active system. I can feed as much as I want to that compartment and watch the results easier. My skimmer pump is pumping 300 gph but I'm only sending 30 gph to the compartment. So the water may make 9-10 passes through the skimmer before making its way back into the main pump compartment and straight to the tank. I'm just amazed that nutrients are so low with 30 gph. And I question if I really need to run 1000 gph through my sump when the pellets and skimmer are only using 30 gph of it. I have a small separate pump setup with a valve so I can feed more to the skimmer compartment if needed.

 

[Randy Holmes-Farley]

FWIW, I too have my skimmer separate from my sump flow, and the skimmer flow is much higher.

 

[eagle]

Ok, Did the test. From 435 to 364 on orp. Tank water is 435 and effluent from biopellet reactor dropped to 364. I'd be interested to see if any others could measure their effluent too. I have been dosing twice a week with zeobak and the pellets seem to be cycled now. I'm going to start adding more water to the skimmer compartment from my little feed pump and see what the orp does. May start slow like 100 gph.

 

[eagle]

One more thing about this is I was having a heck of a time with nutrient levels when I had my DSB and refugium. They were manageable but I would have diatoms at times and GHA in my overflows etc. Getting growth on the glass all the time. It just got to be a real chore to keep it going. And I had tons of macro. So I'm sure my levels were manageable because of the nuisance algae additions. I have rallied against the look of bb tanks and stayed old school for a long time lol. Only reason I tried this is because we had to move the tank in another room while waiting on another tank. When tearing it down the sand/refugium smelled horrid. My wife and I agreed anything that smelled that bad couldn't be good for the system. I've got to say that I'm blown away at how clean the tank is staying and how low the levels are. It is spotless. Crystal clear. I'm gonna stay with this setup when the new tank arrives. I'm beginning to really think my dsb has been holding me back for a long time. Even though I love the look of sand in the tank and sand sifters etc. Maybe a very shallow layer of sand.

 

[Randy Holmes-Farley]

Interesting on the ORP drop.

Is that pH also from the reactor effluent?

 

[Randy Holmes-Farley]

FWIW, I like sand, but only for aesthetic reasons. I think my other methods of nutrient reduction work better than my old DSB, which I removed several years ago.

 

[eagle]

Yes the pH probe went in the cup to. But the lights had just went off before getting home so the pH was dropping due to that.

 

[eagle]

This is the last 7 days of ORP with PH overlay. It's hard to tell by these charts but I was noticing lower high's and lower low's in the ORP each day. While this was happening my nitrates and phosphates were getting lower. So I assumed this was due to the reactor cycling maybe. Of course there are a lot of other factors to orp. What caught my eye was when I slowed the rate through the reactor on the 5th. The ORP didn't drop off nearly as far on the 6th and has steadily climbed with higher lows and higher highs. Also the PH has steadily been higher. Everything has been stable and the same. Dosing calcium and alk via litermeter. It wasn't big changes just noticed a trend. It could just be change in the weather too lol. :squigglemouth: I just like experimenting lol. Watching it a lot closer since adding the biopellets due to many good and bad threads I've read about them. And since experiencing a bacteria bloom the first time I tried em.

 

[Randy Holmes-Farley]

So it is clear the the ORP in the reactor is lower than the tank, and flushing the reactor through faster seems to bring the tank down more.

I'm not exactly sure what is happening in the reactor that is lowering the ORP there, but that may be the normal process.

 

[msderganc]

So I've got a similar situation in my tank. As background, I struggle with oxygenation levels in my tank because my house is very airtight. I've run a line for my skimmer outside, which has helped to stabilize my pH between about 8.05-8.25. I run biopellets in a recirculating reactor, and I have a relatively high stocking level. I feed my 190g ~4 times per day, two cubes in the morning, two in the evening, with two pellet feedings while I'm at work.

For the first six months or so, my ORP was just about 450 (at that point the stocking was light). As I have increased fish, thus feedings, my ORP has dropped. Up until about a week ago, it was averaging about 290. I recently started feeding a bit more, and it is now hovering around 240. No nuisance algae at all, and my water is crystal clear during water changes. I have to clean my glass maybe every 3-4 days. My phosphates sit less than .03ppm, and my nitrates are usually around 2ppm. Corals (mostly SPS) look great, full of color.

My working theory is that the ORP is actually seeing the increased bacterial load from the biopellets. So, as I increase feeding, more bacteria are supported by the system, and thus my ORP drops. Is this valid?

Randy, I know from your article on ORP that it should be used more as a trend, but what is the effect of having a very low ORP (I think I'm getting down there)? Is there an absolute bottom that I should be watching for? How would I correct it if so?

 

[Randy Holmes-Farley]

I don't know at what ORP value I'd begin to worry that something needed fixing. Less than 100 mV, certainly, but above that, I'm not sure.

With increased feedings, I expect there is a heavier organic load and that will tend to reduce ORP.

It is interesting the biopellets lower ORP, but I'm not sure I understand exactly what is happening that reduces ORP with increased bacteria. Maybe increased organics again.

 

[eagle]

Hey Randy, I've watched things over the last month. For whatever reason I'm not seeing the decrease in ORP from the reactor effluent anymore. Your last post is correct though. I have noticed a good correlation in organics and ORP. When my orp is 460-470 my nitrates and phosphates are 0. If I feed heavier I can see the orp over time start to peak and trough lower each day. I've noticed when my orp is in the 420 range my phosphates have been .03 to .05 with a trace of nitrates. If nothing else I'm using it as a tool to measure organics and maybe when my gfo and gac need to be changed. Or at least a test needs to be done.

 

[Randy Holmes-Farley]

THanks for the update.

Enjoy playing with it!

 

[msderganc]

THanks for the update.

Enjoy playing with it!

So, for a few months, my ORP has sat in a range from about 240-270. I tried cleaning the probe in vinegar and the ORP went up to the high end of that range, but still stayed there. Just to see where my probe was reading, I purchased some 400 ORP solution. Immediately after putting the probe in, it went to about 390, and then slowly ticked upward to about 396 after about half an hour. So, somewhat sad that the probe was reading properly, I put it back in the tank.

It went back to 270. AND THEN...it started slowly trending up. No other changes to the tank. As of this morning (12 hours later), it is about to break 300 (and doesn't seem to be leveling off). Maybe my probe was "stuck" in place somehow? I'm not sure how else to explain it.

 

[eagle]

Mine was always in those ranges until I took my sand out. I had a dsb and refugium. I removed both and went bb and biopellets. Orp went to 500 at first. It's at 470 now. Will dip down to 430 if I feed heavy.