adding carbon dioxide

[Charlotte Seibert]

  I read adding carbon dioxide lowers PH, but could also increase alge...two questions..how do you add the carbon dioxide and what do you do to lower the chances of alge other than keep as much sun out as you can?  I just recently cycled and sure don't want alge bringing up that ammonia I worried so much about.

[Vlad Jovanovic]

I really don't think that you want to 'add' any carbon dioxide to your water. Carbonic acid is released all by itself when your microbes are at work. For every 1mg of ammonia they convert to nitrate about 8mg of alkalinity in the form of carbonates are 'consumed' along with roughly 4.5mg of oxygen. So your system  will tend to go acidic all on it's own.

IMO there are much, MUCH better ways to lower your system pH AFTER YOU COMPLETELY FINISH CYCLING (pre-treating your top-up water, or using rain water for top-ups, or using RO water for top-ups, or introducing a source of tannins to your system etc...) should you still feel that you need to. 

[TCLynx]

And if your system pH won't come down naturally, you need to figure out why.  If you used limestone as your media you probably need to change out your media instead of buying CO2 cylinders all the time to bubble CO2 into your fish tanks.  Bubbling CO2 into your system is definitely not a "green" thing to do but it would tend to grow a lot of green but it might be kinda hard on your fish.  And if your tanks tended to run out for a time before you noticed, you would probably be causing some terrible pH bouncing which would also be hard on fish, bacteria and plants.

As Vlad noted, there are better ways.

[Meir Lazar]

I agree with the TC and Vlad, bubbling in CO2 is probably not the best idea for lowering ph.

If you want to release CO2 in the air for the plants, that's different, but the water would benefit greater from enriching it with oxygen, not carbon dioxide.

Lowering PH can be achieved via adding small amounts of very dilute phosphoric acid (in worse case scenario). Usually nitrification is an acidic reaction anyway and would gradually drop ph over time.

[RupertofOZ]

Yeah.. why on earth would you want to bubble CO2 into your tank water... buy yourself a pair of handcuffs... and leave you system alone...

 

If you have algae in your tank... it will produce CO2 during the night anyway... oxygen during the day... and swing your pH diurnally...

 

Grab a beer.. and the remote control... leave the system alone...

[Charlotte Seibert]

I guess the best thing for me to do is stop surfing the web and just stay here for advice...lesson learned... again ty all..My grow media is expanded shale..0 ammonia, 0 nitrite..ph has just jumped in the last 4 days from 7.6 to 8.2.. with no change to the system. We got some rain today, hope more for the next few days.

[TCLynx]

Check your pH early in the morning (like dawn) and then check the pH again in the late afternoon.  See what results you get.

 If your dawn pH is low and your late afternoon pH is high, algae could be the cause of the swings.  Shade water to keep sun out to get rid of algae and reduce the swings.  I say sniff around since anaerobic bacteria often give off very terrible odors.

If algae is not the cause of the pH being high, sniff around to make sure you don't have any grow beds getting anaerobic, sometimes anaerobic bacteria can cause elevated pH.

[Charlotte Seibert]

Did not check the PH at dawn, will in the morning, but even after adding 4 inches of rain water, not sure how many gallons that would be, the heavy rain we had last night added it for me the PH is 8.2. Just added another grow bed yesterday and the older one smells fine. Ammonia has gone back to 0.25, no dead fish, not letting food stay longer than 20 min in the tank, just vaccumed last week, will do it again tomorrow, nitites 0, Nitrates over 180. Plants look good, I transplanted lettus from old bed to new bed, worms looked happy lol, fish look good are eating now not just hiding around the pumps, feed small amounts 2 times a day. Did find one "IN" the pump box, lol, still alive. made sure to cover that extra outlet hole. Will try to post some pictures.

[TCLynx]

Uh, what is the gravel in your system?  Are you certain there is no limestone in it?  I noticed gravel in the bottom of the fish tank, that is generally not advised since fish poop tends to get caught in the gavel instead of getting pumped to the grow beds.

[Charlotte Seibert]

checked the PH this morning still 8.2, my media is expanded shale, the gravel in the bottom is from the established goldfish tank I started with, I will remove as much of it as I can today.

[TCLynx]

Ok with expanded shale the pH should settle down in a while as the system cycles up.  Just relax and be patient.

[Charlotte Seibert]

I guess I dont understand the cycling... I was at 0 ammonia and 0 nitrite...is't that cycled? and my PH was at 7.2 with the same media I have now, the PH rose before I started the new bed.. so how do you know when you are cycled??

[Vlad Jovanovic]

Charlotte, when you can dose your system with ammonia to 1 or 2ppm and within 24 hours be at 0.0 ammonia and 0.0 Nitrites (and can do this for a couple of days in a row)...I think you can then consider your system cycled...