Removed my HOB, CO2 through the roof!

[Blinky]

I've been breaking in a new canister, running it together with a HOB until it had a chance to establish bacterial colonies. Yesterday I removed the HOB and overnight the pH went from ~6.9 to 6.4. My KH is 70ppm, and Chuck's CO2 calculator puts my current CO2 at 48ppm
The fish seemed fine this morning, and I left everything as is during the day - I figured the pH would go up to ~6.6 and I'd remove a 2L DIY bottle this evening to keep it there overnight. Well, I got home and the pH is still 6.4 (it could even be 6.2, they're almost exactly alike on the test kit chart, so it's very difficult to tell). The fish still seem fine (no gasping), and I'm a bit reluctant to cause another swing in pH by removing too much CO2.
Should I leave things as they are, remove a bottle, put an air pump on a timer to run overnights... thoughts?
[edit] Yesterday I did weekly maintainance and did some pretty serious pruning - right now about 1/2 the floor of the tank is planted, 1/2 is bare. There is a huge water sprite (12" wide x 24" high) and a very large tangle of hygrophila polysperma (18" wide x 18" high, 8" deep) in addition to a bunch of smaller stuff, so there's still a lot of plants, but not as much mass as there was. Thought that might be important, since there won't be as much oxygen production going on [/edit]
[edit #2] Okay... I've been doing some checking online, and found some interesting information that seems to indicate that this shouldn't harm the fish (the first thing I found was at http://www.thekrib.com/Plants/CO2/co2-level.html). I have read several places that some fish can tolerate levels up to 800ppm! Unbelievable! I do think I'll remove a bottle tomorrow, but I'm leaving it for now since I don't like making too many changes in a short time unless I have to [/edit #2]

 

[djlen]

What kind of needle valve are you using?
If you can position it so that you can look straight down on it like it's a clock face, close it about 5 'minutes'. This will lessen the flow a bit. Keep your eye on the pH and adjust from there. Try to get it down to a manageable level before lights out tonight. If it's that high with lights on, it'll get higher tonight.
This is an example of how we fear CO2 unnecessarily. Yes, it can be dangerous, but 30ppm/CO2 is just a reference. The fish can get by with a bit of elevation of CO2. It will stress them, but can be corrected with everything turning out OK.
BTW, my levels regularly read '35 - 45ppm' with my semi accurate pH test kit.

Len

 

[Blinky]

Believe it or not, I'm getting those levels using DIY so, no needle valve to adjust (I SO want the real thing, but DIY's what I can afford right now).
At lights out this evening, the pH is 6.6 - so the CO2's at 30ppm - and the fish seem happy, so I'm going to keep a close eye on things but not panic yet .
The plants are covered in little O2 bubbles and I swear they grew inches while I was at work! I can't believe it - I did a double take when I walked in the door. Yesterday I felt bad because the tank looked so empty after pruning, but I don't think that's something I'll have to worry about for too long - look ma, I've figured out how to grow really healthy weeds in a box in my living room, LOL!
As always, thanks for pointing me in the right direction Len

 

[djlen]

You can also adjust CO2 content through surface disturbance and air stones. If you find, in the morning that the level is too high again, you might consider one of these options at night only and then re-adjusting the filter and/or turning off the air stone during the day.
FYI, the first signs of carbonic acid poisoning are sluggishness and loss of appetite, so observe and act where necessary. Until you get the pressurized CO2 you'll have to devise ways to regulate things.
The most dangerous thing is to react too harshly and have large fluctuations in pH. This is very stressful to the fish and should only be used when serious negative reactions are observed.
I once had a heavy duty over-injection in one of my tanks (through my own stupidity) and had one of my beloved Gold Angels laying on his side on the bottom. I did an immediate, large water change and literally had to hold him and swim him around in the tank for about 1/2 hour to revive him. He's fine today, but it scared the **** out of me.
Keep an eye on them.

Len

 

[Blinky]

FYI, the first signs of carbonic acid poisoning are sluggishness and loss of appetite, so observe and act where necessary. Until you get the pressurized CO2 you'll have to devise ways to regulate things.

It never fails, every time you post, I learn something! They ate tonight as if it was their last meal, so they must be okay at 30ppm but I'll be keeping a close eye on things.

The most dangerous thing is to react too harshly and have large fluctuations in pH. This is very stressful to the fish and should only be used when serious negative reactions are observed.

I agree, which is why I hesitated to change anything as long as they seemed okay. I had considered putting an airpump on a timer to come on at night but I was worried that that would actually cause more fluctuation between morning and night pH than just leaving things alone (possibly minus one 2L bottle if necessary). Also the less stuff on timers, the more secure I feel!

Keep an eye on them.

I definitely will.

I had NO idea that going planted would be like starting the hobby all over again - WHAM! right back to the start of the ol' learning curve

 

[m0rl0ck]

Informative post.
And now I'm having doubts about my idea of buying a HOB for my 29 gallon. I dont have any co2 now and am using a fluval 2 internal which barely disturbs the water surface. The plants seem to be doing well on just the co2 produced by the fish.
I have 80 watts over the tank.
Whats the best way to quiet the surface agitation caused by a HOB?

 

[Darkblade48]

Whats the best way to quiet the surface agitation caused by a HOB?

I would try to fill the water up as close to the filter output as possible so that you'd minimize the amount of splashing you get....though of course, it's inevitable with a HOB

 

[djlen]

You can reduce the surface disturbance to practically zero by cutting a piece of filter sponge and then slicing it down the middle and fitting it over the lip of the HOB.
I use this method on two of my filters with good results.

If your plants are doing well, I would leave things as they are. If it ain't broke......

Len

 

[justinb013]

You can reduce the surface disturbance to practically zero by cutting a piece of filter sponge and then slicing it down the middle and fitting it over the lip of the HOB.

Slice it down the middle and slip it over the lip of the HOB?!?!? BRILLIANT!

And all this time I've been struggling with trying to get the things to stay just resting on the bottom of the lip....

Thanks Len, you're the man.