Maintaining Co2 Balance in Large Tank without Ph controller

[Squidly]

I've got the controller probe in one of the sumps of the built in trickle filter which has 300gph running through it with very little head so the results are quick to show if the Co2 injection rate is modified. In addition, i have an Eheim nw pump running full steam at 700gph. So I think the overall flow should be OK. I can quickly drop the Ph by opening the NV. The results are almost immediate.

The tank otherwise is doing incredibly well, better than it ever has since being able to stabilize the Co2 using the controller so I think this should rule out a flow problem.

[Squidly]

IMG_0549.jpg

So I went ahead and setup my Co2 rig using dual needle valves. One to bring the Co2 up to speed within 2 hours and the other to maintain the Co2 rate at a constant level so as to eliminate the need for a ph controller. Despite the gaggle of fittings, I have to say that this did the trick. One valve runs open at an increased clip while the other at the pre-tested constant rate two hours before. After 1.5+ hours, I turn the first valve off and let the other continue on which brings the Co2 to the desired level by the time the lights come on.

Thought it worth mentioning that initially I ran a second separate nw pump in the tank and found that there wasn't any appreciable difference in the amount of time it took for my tank to get up to speed (as compared to running out a single source with increased Co2 output). As a final check, I tried maxing the surface agitation but discovered that it I only used more Co2 and couldn't get the ph below 6.3 (which isn't low enough for my needs).

Now that the Co2 is perfectly balanced throughout the day with the fluctuations of the controller, I do see improvement in the plant growth and the fish no longer flashing the plants from time to time. Now I just have to remind myself not to change the lighting height or surface agitation without adjusting the NV...

[Matt F.]

This may have been mentioned, or maybe it's old hat, but why not use two diffusers at opposite sides of the tank with two needle valves? This way you can have equal injection on both sides of the large tank. I thinK ADA recommends this with their larger tanks.

Edit:
opps didn't read the last post!

Glad it's working out for you.

[Squidly]

I have a tube extending the length of the tank with additional flow pushing towards one end, or close to 10x. Since I now had separate controllers, I tried putting another NW DIY pump on one end. I didn't notice any appreciable difference in the time involved. When i pushed the injection rate much further with either one or both setups, I get larger Co2 bubbles that just head to the surface. While I might be able to get to the desired Ph level within a hour, I think I'd be wasting a lot of Co2 trying as opposed to waiting it out for 2 hours. Weird, I know all too well.

Before the NW's, I used dual DIY reactors and atomizers. The result was always nearly the same. I went so far as to bypass the built in trickle filter before discovering a bad solenoid that was leaking and going back to it. Without the controller, i was always shooting past or coming up short of the mark giving me real problems. Using dual solenoids and NV's seems to work.

[samh]

Hey squidly,

I had/have a similar problem, where i would set the NV during peak demand, halfway during the photoperiod and using the ph controller to monitor the co2 only. I also found that it would take to long to reach my optimal level.

I then went on a big fad of trying to build huge reactors and massive flow through them and the tank still didn't gas up any faster and plant growth diminished. I then cut out most of my flow and set up the ph controller again with very open NV to reach the ph level as fast as possible from co2 on in the morning 45 min before lights on, and then it turns the solenoid on for 10min every 45min during the day. The plant growth is the best it's been.

However,

I know that the set-up has flaws, because
1. of the extreme bubble rates i need to gas up the tank
2. The amount of co2 i use, on average a 6kg co2 cylinder only lasts 2 months

Identifying the areas to be improved is one thing, solving them is another.

[Tom Barr]

The ATI fixtures have dimming functions so the CO2 ramps up the same time period as the light intensity.

So when the lights come on, so does the CO2, over the next 2 hours, the CO2 increases like the light, then peaks, and about 1 hour before the lights go off, the CO2 is turned off.
It takes about 30 min for the tank to degas, but by then, the plants have had their fill and the light is low.

[samh]

Hey squidly

Forgot to mention I run multiple reactors and NW pump combined.

[gsjmia]

All my tanks lack pH controllers, but I keep a pH meter handy, made a special end cap with a silicone ultra thin membrane for a 4Kh Reference. Acts like a CO2 probe. Takes about 5 minutes to settle.

Tom, can you provide a source for the ultra thin membrane. It seems pretty expensive.

I did find this .003 thickness membrane-is that too thick?
http://www.sspinc.com/ssp_store/Thin..._to_040_21.htm

Your end cap is filled with 4kh reference with no air gap, correct?

If your lag time is only 5 min, why not connect your probe to a PH controller?

[Tom Barr]

Tom, can you provide a source for the ultra thin membrane. It seems pretty expensive.

I did find this .003 thickness membrane-is that too thick?
http://www.sspinc.com/ssp_store/Thin..._to_040_21.htm

That's the place I got mine.

Your end cap is filled with 4kh reference with no air gap, correct?

the KH itself is arbitrary, as long as you know what it is to a precise ppm, you can calculate(well as long as it's not infinity or zero or near zero)

If your lag time is only 5 min, why not connect your probe to a PH controller?

Because control functions only WHERE you place the CO2 probe and well, I have little need. I have to calibrate the sucker, and make sure the membrane does not foul, replace the cap, check to see if it leaked or what happens if the membrane torn and I jammed a ton of CO2 into the tank suddenly?

I'm more interested what the CO2 ppm is AFTER the FACT....in a nice well growing planted tank. Few hobbyists EVER approach things this way and thus learn very little.
They come in with a conclusion 1st.then see if they can find aquariums that fit their idea.

I come in much more ignorant, I look at the aquariums doing well, then I measure them and collect the data, only then..........do I, can I....... make any sort of deductive reasoning/conclusion.
In some tanks, it was 70-80 ppm, others maybe 40ppm. Another 55ppm.

It also depends on WHERE I took the reading, How long I took to get the stabilized reading etc.

If for example I took a reading at the back of the tank, often where folks place such devices, out of the way hidden behind plants,.......when those plants grow and cover the probe, the CO2 goes way down locally, so the pH controller will add a lot more CO2 to try and make up for that.
Even if the demand for CO2 is only slightly more/higher.

It's just another way to control the system using a lighting controller instead of a pH controller and CO2 probe/KH cap.
One I've NEVER seen anyone suggest.

[gsjmia]

Tom, I was reading the MDS on the ultra thin membrane at SSP and I don't understand the math-is it permeable enough to give a reasonably quick reading?

Is the gas exchange bi-directional so that it will adjust up and down? Or is it an asymetrical C02 roach motel.

I believe you about the PH controller and placement (but its so enticing I can't leave it alone!)-- if you put the C02 probe/KH cap in the sump of a 400gph wet/dry, wouldn't that provide a good average C02 reading?