Maintaining Co2 Balance in Large Tank without Ph controller

[Squidly]

After two years of trying, I still found it impossible to maintain the Co2 level in my 100g tank. Although I tried turning the Co2 on 4 hours prior to lights on, I still wouldn't reach any target consistently several hours after lights on. Only after installing a Ph controller more recently have I been able to maintain the tank without turning it into a BBA zoo.

So I then set the needle valve to maintain my target Ph (6.15) throughout the day running open (so as not to turn off the Ph controller). This worked really well except in the morning I discovered that as before, I couldn't arrive at the desired Co2 saturation level at lights on unless I started many hours prior. For whatever reasons that I can't discern, the tank requires a Co2 boost initially to bring it up to speed. Once there, it can be maintained with a much smaller amount of Co2 being injected quite readily.

If I am to be able to break from the Ph controller dependency, my solution (which I hate because these things always cost more money) is to install two solenoids, and two valves each running on a separate timer. One to be run more open for one hour to achieve the desired level, and another to take over and run open throughout the remainder of the day to maintain it.

I guess my question is this how it's done for large tanks, or am I injecting too much Co2 or? The fish are fine and things are really growing like mad and I couldn't be more pleased. No reason really to mess with it other than to lose the Ph controller. I could always dose less Co2, I just don't want to deal with the algae again now that things are going so well.

I've got good flow running around 10x overall and good mixing etc. Running Eheim 1103 NW w/venturi through Nu-Clear canister. Separate 300g pump pulling through internal trickle filter (sealed)

Thanks

[dutchy]

If you can't reach the target with that much lead time the capacity of the setup is too low, simply as that. i used a pH controller before until it started to show erratic values and melted most of the plants. I threw out the controller and have been doing without since, but it worked well for a long time. I also knew that with continuous CO2 addition I had to slow down the rate of addition in the morning. Now there was no pH controller that shuts it off at the desired level. Theoretically that would mean that I couldn't reach the desired level before lights went on. I compensated that by slowing down the rate in which the lights turn on. Before that was 30 minutes, now it's two hours. Less light = less CO2 demand, so it's easier to reach a higjer CO2 level. It has worked well, no signs of BBA. I even inoculated the tank and it just died.

I've used a pH controller for years but it's another single point of failure and can be done without.

[Squidly]

Thank you, but I think something else is going on? I can very easily reach the target dose, perhaps in 15 minutes if I tried - but I can't maintain it at that rate without going past my target dose is the problem.

For example I can set the controller to reach a target of X.X. Once there, I can back off the amount of Co2 being injected so as to keep it constant and just above shutting the controller off. Then the next morning, allowing perhaps two hours of Co2 to be injected before lights on, it will still be several hours before the target is reached. The only thing I think of is that my fish, those that survived two years of up and down Co2, are fairly hardy by now and therefore have too much Co2. I've backed it off 1.5 degrees to see how it goes. I wait 3 hours before turning all the lights on and then off an hour before they are all off (thx).

I have the controller because regardless of the method (having used dual reactors/atomizer/diffusers), this long lag time to achieve the target kept me from having any success. For a great while, I'd had a leak in my solenoid but never could find it. Thought I'd have this licked by now, but no!!! I understand the limitations of the controller, and in this case, its usefulness.

I should think someone who has a tank this size might have had similar troubles. I'm betting on too much Co2, at least as long as the algae stay gone. Otherwise a manifold and second solenoid I think would be my last option.

[nipat]

In case you haven't read this thread. It seems possible to reach target level fast
and stay there without pH controller or double the injection at starting time.

http://www.barrreport.com/showthread...ble-enough-CO2

[Tom Barr]

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.

[Squidly]

Well, if I adjust my needle valve in the slightest Tom, I can see the difference on my controller readout within a few seconds of doing so (I find the Reef Fanatic Ph Controller to be very fast and stable for what it's worth) - assuming the range for testing is within +- 5 degrees. At the extreme ends one must wait perhaps 15 minutes in my experience.

Per the thread Nipat, I am totally lost as to what the solution you describe was?

Thanks all!

[nipat]

Per the thread Nipat, I am totally lost as to what the solution you describe was?

Thanks all!

In summary, the OP (who is fortunate to have an Oxyguard CO2 meter) had
problem about CO2 taking long time to reach the optimal level.

Tom saw his graph and said it could be better, and showed his graph
which described reaching the level fast and staying stably there, without using
pH controller. Tom also noted the OP's CO2 level stayed too high at night.

The OP had used a pH controller too. You can see the graph in the first page
which is like what you described (reaching target level fast and being cut
from time to time when CO2 was too high).

At last the OP could duplicate Tom's graph by increasing flow, upping BPS,
and heavy surface agitation.

[the last picture in the post #20]
http://www.barrreport.com/showthread...5110#post75110

I think the thing that prevented CO2 from going too high (without using pH controller)
is heavy surface agitation. And the agitation helps in solving high CO2 level at night too.

BTW, the idea of doubling the injection at starting time by an additional solenoid
is very good in efficiency. I may copy it myself.

[nipat]

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.

Ah, CO2 probe for the rest of us.

[Tom Barr]

Well, if I adjust my needle valve in the slightest Tom, I can see the difference on my controller readout within a few seconds of doing so (I find the Reef Fanatic Ph Controller to be very fast and stable for what it's worth) - assuming the range for testing is within +- 5 degrees. At the extreme ends one must wait perhaps 15 minutes in my experience.

Per the thread Nipat, I am totally lost as to what the solution you describe was?

Thanks all!

It is not the controller that's the control critical point, it's the flow and CO2 mixing throughout the tank, it also depends on where the pH probe is placed.
pH controllers in a small volume space with ample flow through are not an issue.

[Squidly]

Well Nipat, as suspected it took over 3 hours (probably 4) to load up even at a somewhat reduced Co2 level. While I suppose I could take it further, then I'd be raising lights and all that.

While I think the process to increase surface flow might be the remedy per the thread (and thanks for the explanation), I have a lot of plants which hit the surface. I found that I was getting brown algae when I increased the surface agitation too far. I do still have reasonable surface agitation along with 300gph going through the trickle filter (which was previously run open with little difference in Co2 loss) so I should think I'm getting the o2 in there.

Hate to have to spend more $$$ on another solenoid and manifold, but I don't see any other way.

Co2 is a lot trickier than I ever imagined.