CO2 System Request

[farm41]

I really don't like them either, but they are there to work. I only buy small ones 1.5-2" and trade them back when they get larger. You are right though, when they get older they get lazy and to hyper, the small ones though do a good job on the algea.

No experience with AFF.

 

[jowens]

Randall,

If you follow this diagram below, you can go to any welding store and get the equipment for your CO2 tank/regulator:

http://www.csd.net/~cgadd/aqua/diy_co2rig.htm

I agree that if there's any place to spend a little extra, it's on the regulator. The needle-valve is essential too...but it's not a complicated "part," so you won't need to invest cash much there. Just make sure you have a decent one.

I set up my whole system for about $170. It works great. With the size of your tank, lighting, etc...it sounds like you're not afraid to invest. So you might as well do it right.

Rather than get into tons of specifics about the holy trinity of kH/pH/CO2, I can just tell you what I do in my soft water tank. The water out of my tap is about 1kH (yes, I know I've been blessed). My CO2 tank outputs about 30 bubbles per minute, directly into my Eheim intake (I have a little trick for doing this well). In order to avoid an excessively low pH (the carbonic acid from CO2 injection lowers pH), I use baking soda during each water change to raise my kH to 3. Keep in mind that in a non-CO2 injected tank, a kH of 3 would result in a pH of about 7.2.

With a kH of 3 and a bubble rate of about 30 CO2 bubbles a second, my pH ends up at 6.5. Now if you look at the chart below, you'll see that my CO2 levels are quite high (out of the "good" zone and just into the "danger" zone). Despite being this high, I've never had a problem with fish loss and my plants are quite happy. But my sitution is probably not perfect.

http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm

I think the perfect situation would be to set your kH at 2. Then if you add 24 ppm of CO2 (the perfect amount), you end up with a pH of 6.4. Trying to measure the actual CO2 levels using test kits is kind of pointless, IMO. What you want to do is set your kH level at 2 by slowly adding baking soda. Do this just as you're starting to add a modest amount of CO2...probably about 20 bubbles a minute, directly into your canister filter intake. Wait a few hours, then measure your pH. If you get 6.4, then everything is perfect (meaning: you're getting exactly 24ppm of CO2 into the tank). If you get a somewhat higher pH level, then you need to add a little more CO2. If you get a somewhat lower pH level, then you need to reduce your CO2 a little.

You can use either the kH or the CO2 to adjust the pH - but as a rule, you want to always think long and hard before adjusting your kH. It's a rather permanent decision (until your next water change), so if you want to simply tweak your pH a modest amount, it's generally easier to increase/decrease the rate of CO2 bubbles. Then if you make a mistake, it's easily correctable. More bubbles = lower pH. Fewer bubbles = higher pH. Just make these changes slowly.

This initial stage of experimenting can be tough on fish, but they should survive just fine, as long as you resolve things quickly without doing anything dramatic. Most fish can survive one or two pH fluxuations...it's the constant changes that hurt them. Once you figure out your levels, you'll see that it's all quite easy. You keep the kH exactly the same for all new water you're putting in. You keep the bubble rate the same for CO2 going into the tank at all times. And presto! Your pH will never move, not even a little bit. The key is deciding what levels you want, then sticking to them.

pH "crashes" due to CO2 injection are a huge myth. If you keep the kH constant and the CO2 constant, the pH will not only stay constant, but you'll be able to predict it down to 0.1 of accuracy. And by adjusting the CO2 bubble rate, you can manipulate pH extremely precisely. More precisely, in fact, then you can with almost any other method.

It's all about chemistry, baby.

 

[Randall]

Thank you

Dear Jowens,

Thanks very much for all the good information.

My concern with using baking soda or the equivilent to raise KH levels is its adverse effect on conductivity. The fish in this particular tank spawn like there's no tomorrow. The highly successful hatch rates I've been experiencing is due, in part, to low conductivity, allowing the eggs to be fertilized and develop properly. Would it be beneficial to not buffer the water so much and use less CO2?

Thanks very much.

Randall Kohn

 

[aspen]

high co2 levels are ok, when you have full control, and you want to get your tank going through quick developement and growth phases. lower levels closer to 10 ppm, will sustain a tank very nicely. having the ability to change these levels easily can be a great help when battling algae. your plants will still pearl at 10 ppm, but the higher the co2 level, provided there is lots of light and other nutrients, the faster the growth, and will really get things growing well.

adjusting co2 levels is a good way to move your tank in the direction that you desire. if you come to the point where all of the plants look great, and the tank looks full, but not overfull, slowing the co2 will keep things this way for longer, allowing longer periods between prunings.

rick