Ph keeps falling...

[fastfly48]

Hello all.

Not long ago I started injecting pressurized CO2 into my 20g planted community tank. I want to keep the CO2 on for 24hrs a day but can't because I've been having trouble keeping my Ph from falling below 6 with the CO2 on for only 10hrs a day. I can only imagine what would happen if I left it on all the time.......

My Kh is 50ppm so that's ok-ish....but with the Co2 bubbling away for a 10hr day (at less than a bubble a secind) the Ph drops to 6. Without the CO2 on the Ph is around 6.8-7.
I'm not sure if the Ph can drop lower than 6 becasue by the time it gets down to 6 the fish, understandably, start having some troubles, so I turn the CO2 off.
Shouldn't the Kh determine the starting AND stopping points for Ph?
Why is my Ph falling so low?
I guess that a hell of a lot of Co2 is getting dissolved into my water? But how do I decrease the amount dissolved? I've tried decreasing the bubble rate but that doesn't do it.
Oh and I don't have any buffers present either...
Hope you can help....and thank you for your patience.
Ry.

 

[Lance M.]

Adding CO2 causes the pH to decrease.

I can't really tell you what the best way to increase the pH. I've heard adding small amounts of baking soda (can't remember, correct me- I'm probably wrong) or something helps.

Rainwater has a pH of around 5.6°.

 

[fastfly48]

Thanks Lance.
Yes I know CO2 decrease the Ph. It's just that it's pulled mine down HEAPS.
I was hoping I wouldn't have to be adding Baking soda all the time...
Somethings not right.....

Thanks again.
Ry...the NOOB...

 

[malkore]

Well, you're sitting at the bare minimum Kh level for safe CO2 injection, so your pH will move a lot more easily than, for example, my tanks, which have about 3x the Kh as you (you're a smidge of 3dKh, I'm about 9.5-10dKh).

I wouldn't think that a 20gallon with a low Kh should need more than about 30 bubbles per minute. I would try resetting your bubble rate so you get 5 bubbles in 10 seconds, and see if that helps.

Does your regulator have a solenoid valve, that you plug in to an electrical outlet? You can buy a cheap lamp timer, and run your CO2 on a timer so you don't have to manually turn it off all the time.
The more expensive option is a pH controller, which will monitor your pH and shut off CO2 when you hit, say pH of 6.4 (about 36ppm of CO2 at 3dKh).

Kh does represent buffering capacity, but it doesn't define a hard pH 'stopping point' for CO2 injection.

 

[fastfly48]

Solenoid valve? Um....if I have one I didn't know that's what you call it....
I have a valve...but it's not electrical or anything....just a manual nob really.
I'm hoping on being able to leave the C02 on most of the time...
Im just trying to get my Ph stable now. Tricky stuff!

Ry.

 

[Simpte]

Sounds like a needle valve, not a solenoid. Could you post a pic of your setup?

 

[fastfly48]

um...ok I'll try.
ry.

 

[muddlehead]

im pretty sure you cant leave CO2 on all the time, when you turn off your lights your plants stop photosynthesizing and they dont absorb any CO2 which means your ph drops quickly, thats why people put their CO2 setups on timers, if your regulator doesnt have a selonoid on it i think you can purchase them for pretty cheap, and it should be a quick install if you have the tools

 

[Purrbox]

Actually many people run their CO2 constantly. The key is to watch your fish and make sure that they are OK first thing in the morning. If no one is gasping at the top of the tank you are maintaining sufficient O2 saturation during the night and don't need to worry about it.

Of course you're much less likely to inject too much CO2 when using DIY than when using a pressurized setup. The same principal applies to both. My understanding is that most people turn off the CO2 at night more to conserve their CO2 and reduce how often the have to refill the tank, than because of any danger to the fish.

The situation here sounds more like an issue of getting the injection rate set to the right level than anything else. Once the right bubble rate is found the PH won't get pushed as low, and both plants and fish will be happy.

 

[fastfly48]

Thanks for all that.
Yeah...it's pretty harf at the moment becasue I have to turn the system on and off....so in the mornings I spend quite a bit of time just trying to get the bubble rate right. I'm trying to get the rate just right so that I can leave it on 24/7.

However, I've found that I can do that....it's just that it leaves me with a C02 level of like 5ppm, and that's rediculous considering.
I don't mind how quickly I go through the C02 because I'm getting free re-fills...SCORE! So my main objective is too find a balance with it. Very tricky. It's so messy and un-controlled fideling mannualy with the shut off valve.

So if I leave it on 24/7 the Ph is going to swing anyways hey?...becasue of the day-night situation. THe Ph will be higher during the day and lower at night. I've just got to find a way so that the Ph doesn't get too low and night, but still have nice C02 levels (15-25) durnig majority of the day.....
Hmmm.....