DIY CO2, Cardinal Tetras and my planted tank.

[paranoid1123]

My cardinal tetras don't seem to like my co2. I let my diy co2 run 24-7 but at night I have a air stone going to let the co2 out. During the day when the air is off the tetras scrape the sides of the tank like they are trying to get out but at night they swim all around. My ph when the air is off hovers around the 6.0 range. But at night it is more like 6.7. What would be best to keep the tetras happy? Should I just ditch the co2? My plants really like it. I've noticed them
Being alot greener with it. What should I do?

[wesleydnunder]

When I added co2 to my tank I tried to keep the co2 at around 25 ppm. My fish didn't like it higher than that. Sounds like you may be over 30 ppm. What is the ph of the water out of the tap? Let the water sit in a cup for 24 hrs, then check the ph. This is your baseline. Dropping the ph with co2 a full log gets you in the 25 - 30ppm ball park. DIY co2 is very difficult to maintain co2 levels. I used it when I first started, then ditched it for pressurized because I didn't like the fluctuating co2 level.

Mark

[Mzungu]

How big is this tank?

I'm curious as to why the tetras are swimming all around at night. Is there a lot of light at night in this tank's room?

I would be worried if the tetras were gasping at the surface while the CO2 was running without the airstone. But you say they're scraping the sides of the tank, as if they're trying to get out. How long have you had them? It sounds like they're still a bit nervous, and getting used to their home and any activity around it.

Edit: And +1 to Mark's post. He's the CO2 guru.

[paranoid1123]

i should clarify my lights come on @ around 10 am. from the time the sun come up till then i can see the fish just swimming peacefully around. ive had the tetras now for about 2 months i don't think they are nervous. also marks post was written way to high tec. for me please dumb it down for the lay people? ( a full log) and how do you test your co2 ppm? im looking into geting a pressurised system but still don't know how to set it up. i need a step by step guide for noobs.

[wesleydnunder]

I just wrote a page long post explaining the co2 process for you paranoid, which the forum proceeded to eat. two things occur right now; I have to go back to work and I'm pissed that 30 minutes of writing just evaporated. Anyway, when I get back to the office after a while I'll try writing it again in Word, then save it.
<grumble>

Mark

[paranoid1123]

thanks. i understand how co2 works i just don't know how to test co2 saturation. and i don't know what a log is.

[marauder_77868]

pH is a logarithmic scale...thus a full point (or a full log) represents a change in the number of ions in the water by a factor of 10

[mgarrido]

the best way for know what are you doing with your co2 is a drop checker, if you want something for dummies go with the red sea drop checker
co2indicatorbh7..jpg

Also you can use a kh meter test from API, just follow the instructions.

[wesleydnunder]

The forum won't let me post this for the second time. I guess I need to post something in website feedback. GRRRR

Mark

[wesleydnunder]

i should clarify my lights come on @ around 10 am. from the time the sun come up till then i can see the fish just swimming peacefully around. ive had the tetras now for about 2 months i don't think they are nervous. also marks post was written way to high tec. for me please dumb it down for the lay people? ( a full log) and how do you test your co2 ppm? im looking into geting a pressurised system but still don't know how to set it up. i need a step by step guide for noobs.

OK, first ph. The ph scale is from 0 to 14. Pure distilled water has a ph of 7, called neutral. Ph below 7 is called acid. Ph above 7 is called basic. Water is made up of hydrogen ions and hydroxyl ions. If there is an equal amount of hydrogen and hydroxyl, the ph is 7. More hydrogen ions than hydroxyl and the solution is acid. More hydroxyl ions than hydrogen and the solution is basic.
The ph scale is a logarithmic scale, which means each step is a factor of ten away from the one next to it. Example: a ph of 6 is 10 times more acidic than a ph of 7. A ph of 9 is ten times more basic that a ph of 8. When I wrote “drop the ph a full log I meant to add co2 until the ph drops from your baseline, (we’ll say 7.8 until you test it) to a full log lower (to 6.8 if your baseline was 7.8).
To find your baseline draw a cup of water from the tap and let it sit out for 24 hours, then test the ph. This is your baseline or starting point.
When you add co2 to water it forms carbonic acid and lowers the ph of the water. Testing ph tells you how much co2 you’re injecting. At a rough guestimate, dropping the ph a full log will give you roughly 25-30 ppm of co2. Dropping the ph .8log will give around 20-25 ppm of co2. As Mgarrido pointed out, a drop checker will help you more accurately measure how much co2 is in solution.
There is a chart on the web by Chuck Gadd that compares KH, Ph and co2. If you know your KH and your ph you can calculate what your co2 sat is. This chart assumes that your KH, your water’s buffering capacity, is made up of only carbonate. If your water contains other buffers it throws the chart off and renders it effectively useless. I think this is why it was suggested to get an AP KH test kit.
You can make a KH solution with distilled water and baking soda that will help you in making your drop checker. 1 degree of KH is equal to 17.6 ppm of carbonate, or 17.6 mg/l. A solution with a KH of 4 is commonly used to make drop checkers.
Since DIY co2 systems really have no way to adjust the co2 going into the tank, the co2 is seldom steady or where you want it. That’s the main reason I junked it in the first place.

Mark

[Mzungu]

So, what about tanks with AquaSoil as their substrate? I've noticed that AS really drops the pH in a tank. Should you use your tank water without CO2 as a baseline instead of tap in this case? Does that make sense?

To clarify, if I set out a cup of tap water for 24 hours to get my baseline and then tested a tank without CO2 but with AquaSoil, the pH would be drastically lower even without CO2. I know this way of measuring CO2 isn't extremely accurate, but that situation just popped into my head as I read your post, Mark. :)

[wesleydnunder]

I've never used aquasoil MB, so I don't know if the acidification goes away after a while like the ammonia does?

If the substrate KEEPS the ph lower then I'd say use the lower ph as the baseline.

Mark

[TheOldMan]

I understand that aqua soil has peat in it so that is why it lowers the ph and should go away in time.

[blacksmith37]

When I had salt tanks (and a lot of caulerpa), the pH would change from day to night due to CO2. To get a baseline pH , I simmered a water sample in the microwave awhile , this drives off (to a very low level) CO2 (and other gasses) and gives an intrinsic pH.
As I remember the first H comes off at pH6 , leaving HCO3- :the second H doesn't come off until pH 10 , leaving CO3--.

[wesleydnunder]

Good point about the macro and the co2 swing from day to night. Planted FW tanks do the same. Complete degassing via heat may give the intrinsic ph, however, water that has sat in a cup at room temp for 24 hrs is naturally going to have some co2 and o2 in it. To my thinking, this is a more realistic number from which to start our target co2-injected ph than the intrinsic value.

Mark