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first off i would like to say hi to all here at APC, i just found out about this forum and have been looking at some post and there is a ton of info here. anyways im new here but not all that new to planted tanks.

so to get to my question, my most recent setup is a 90 gal community setup which i just planted 4 days ago. my problem is that the pH is not being lowered by the injection of co2.i have the pH controller set to turn off co2 at 6.5 but it never reaches anything below 6.9 and it hardly ever stays there.....usually around 7 to 7.2 i have an external reactor plumbed into the output of my sump filter. the reactor is a diy one i built almost exactly like the design of the one posted in the diy forum by gomer. I know there is many factors effecting ph but i have gone through everything i can think of. anyways here is a list of my setup.

90gal w/overflow and 29 gal sump (sump is10-15 gals full)
2* 150watt MH 6500k lights
flourite substrate (avg 4" depth)
600 gph return pump
milwaukee pH controller and co2 regulator(w/needle valve, solenoid & bubble counter)
RO water ( reconstituted with seachem equalibrium)
silicon tubing from regulator to reactor

inside the tank i have a piece of diftwood and some petrified wood stones .... but nothing that would raise the buffering capacity.
for media in the sump i am using lava stone. i thought i might be the culprit but i put a couple of pieces some ro water overnight and it never changed ph or raised the KH
here are the water parameters in ppm
ammonia 0.0
nitrite .25
nitrate 3.0
phosphate 0.2
gh 3 deg
KH 2-3 deg

also i called milwaukee and their rep had me test the controller and the probe and they are both working fine.

the sump is designed for minimal surface agaitation ...it does not have a drip plate, and has a lid which is taped shut to not allow gas to escape. ( i got the design from a filter phil edwards built, on another forum.)

there are very very small bubbles coming out the output into the tank. so i thought maybe the reactor wasnt diffusing the co2 effectivly into the water. but my reactor has more bio balls than the ones i've seen on here and is about 14" long. .

well i know that is a long first post but any help would be greatly appreiciated ....i've talked to a rep from seachem and said he had never heard of something like this before .... so please if anyone knows anything about this please reply
 

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Vance,
What's the bubble rate your needle valve is set for? Are you saying that the pH doesn't lower significantly even if you up the bubble rate? If the controller is never reaching the set pH level of 6.5 to shut off, then it sounds like you're not injecting enough CO2 to compensate for whatever loss your sump is inducing.
 

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Discussion Starter #3
bill- i've tried different settings with the needle valve.. but its been kept at around 2-3 bubbles per second with virtually no change in ph ...but no there is no significant change when i up the bubbles per sec.
 

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Going by elimination, I'd remove the controller and have the CO2 running 24/7 without it, this will eliminate any chance that the controller is not setup correctly or not working right. My guess however is that the overflow is outgassing it all, it doesn't matter if the sump is sealed or not, the air is being sucked into the overflow and outgassing is occuring in the pipes going from the overflow to the sump. I'd suggest converting to a closed loop temporarily to see if the CO2 levels do come up, confirming that your problems do lie in the overflow/sump setup. If that's the case the only solution that makes sense to me is removing the sump and overflow and to use a canister filter. You can also try to reduce the flow, this might help. I use a 'stockman' design standpipe in my reef tank and that greatly reduced the amount of air being pulled into the pipes, but I wouldn't say enough for a CO2 injected planted tank.

hope that helps
Giancarlo Podio
 

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Discussion Starter #5
thanks giancarlo.... i guess running it as a closed loop is about the only choice i got right now...thanks for the idea... i would unplug the controller but since the pH never drops below 6.9 the solenoid never shuts c02 off so theres not much point.

im not sure what you mean by stockman pipe......the pipe i made was after a design i saw on a website ...its called a durso- standpipe i believe....it has a upside down elbow where it siphons water out of the overflow .....is this the same as a stockman?

the thing that makes me wonder is that i've heard of a lot of people using sumps and " wet drys" for filters on c02 injected tank.... and i've never heard anyone else say they have this problem...

does anyone else out there use a sump filter on a c02 injected tank with an overflow?????? if so do you ever have this problem ....thanks for the help :wink:
 

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vrl7526 said:
thanks giancarlo.... i guess running it as a closed loop is about the only choice i got right now...thanks for the idea... i would unplug the controller but since the pH never drops below 6.9 the solenoid never shuts c02 off so theres not much point.
Very true, however it was just to eliminate the possibility... but if the solenoid is always open it's likely not the problem.

im not sure what you mean by stockman pipe......the pipe i made was after a design i saw on a website ...its called a durso- standpipe i believe....it has a upside down elbow where it siphons water out of the overflow .....is this the same as a stockman?
Stockman and Durso standpipe designs are somewhat similar in purpose (reduce gurgling noise). I found the stockman to be more adjustable and seemed to work better for me, but they are very similar designs. Do a search on the net, you'll find pleanty of references.

the thing that makes me wonder is that i've heard of a lot of people using sumps and " wet drys" for filters on c02 injected tank.... and i've never heard anyone else say they have this problem...
I haven't, sure in reef tanks but not in CO2 planted tanks. I know of a couple off hand but they all had similar issues or were injecting more CO2 to balance the loss.

I think a canister filter would be the quickest and more effective solution however you can play with the pump rate of the sump, the slower the better. If you have a gate valve on the intake you can adjust it to nearly eliminate all bubbling but you risk restricting the flow too much and emptying your sump.

Hope that helps
Giancarlo Podio
 

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http://www.dursostandpipes.com/ For the curious.

I've used a sump for years and before that, a trickle filter. I think it was George Booth that did some study that suggested only a marginal loss of CO2 with the use of wet-dry filtration. If you have a controlled, pressurized CO2 system, you should have no problems.

The reaction of pH to the addition of CO2 is chemistry and somewhat predicatble. From what you describe, I would suspect a faulty pH probe or your KH reading is bad. I assume you've tested the probe. What test kit are you using for the KH?
 

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Also, if your overflow provides, I've converted from the Durso/Stockman to the siphon drain. You add a gate valve to the hose from the overflow to the sump and adjust it so that a siphon is created. Once this happens, you will not get the dreaded toilet flushing sound from the overflow and the gurggling in the sump. This also minimizes surface agitation in the sump thereby reducing CO2 loss.

As a safety feature, people convert the return typically found in the overflow to an additional drain line just in case the other gets clogged.
 

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Discussion Starter #9
sorry its taken so long to reply but thanks for all the help you guys

giancarlo- i did run it as a closed loop and as you suspected i began to see the ph lower within half an hour.... so my problem lies in the overflow and sump.

also i've used a seachem alkalinity test and a aquarium pharmaceuticals kh test....both get close to the reading ...around 2-3 degrees.

i decided the quickest way to solve this problem is to get a canister filter ....i just ordered a eheim the other day and it should be here soon ....

thanks for all the help
 
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