Pressurized co2 in heavily stocked tank?

[mattmathis]

I'm going to order my pressurized co2 this weekend, and I have just a few questions please...

I've been reading everything I can to try and get ready to get it going when it gets here, and I came across an article about CO2 not being safe for the fish if it is a heavily stocked tank. Is that true? Also it said something about if it is a covered aquarium (glass tops) the co2 will form a layer in between the water surface and the glass and prevent oxygen from entering the water. I have to keep mine covered because of cats. lol Opinions?

Also, what is a good ppm of co2 to start at? Should I start low and work up or something?

Thanks!

Stocking (75 gallon):
With Eheim2217

2 Angelfish
12 tetras
4 cories
1 dojo
4 dwarf neon rainbows
1 red tailed shark
2 botia striata
1 common pleco

 

[An t-iasg]

Generally, aim for 15-25 ppm CO2. Some people go up to 30 ppm CO2. Here's a good article and chart to determine your CO2 level:

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

Starting out at one bubble per second was a good rate for my tank, but your tank is bigger than mine so you would probably need a faster bubble rate.

I never heard anything about CO2 being dangerous in a heavily stocked tank. CO2 does not displace O2 in the water. The plants will give off oxygen as a part of photosynthesis. But if the fish are gasping at the surface of the water in the morning, put your solenoid on a timer and have it go off at night (assuming you don't have a pH controller as a part of your CO2 setup).

I have glass tops on my tanks with pressurized CO2 and I never had a problem. I had bettas that come up to the surface to breathe and they were always fine.

 

[ricardo48]

I think its worth mentioning that IMO you do not have a heavily stocked tank.

I have almost more fish than you in my 15 gallon tank and I run co2 at 35ppm so I dont think you are anywhere near heavily stocked.

 

[timwag2001]

stocking doesnt matter. you can cover your tank just make sure it isnt air tight. allow for gas exchange.

like was mentioned above, co2 doesnt displace o2. but you can over do it.

get yourself a drop checker with 4dkh solution. make sure it stays green. if you have a very heavily planted tank you can get away with putting a little more co2 in there just be carefull that your fish arent showing signs of stress. that chart is ok to get you in the ball park but can be thrown off w phosphate buffers. so they arent all that accurate.

i have a ph controller that is hooked up to a timer that comes on an hour before my lights come on. that way the co2 levels are at optimal levels before my lights come on. and i have a airstone on a timer that comes on when my lights turn off

 

[ricardo48]

I must mention about this more.

I hate the PH/KH chart for calculating co2 and think its relied on too often.

My PH is currently 7.3 and KH 14 which according to the chart is 20ppm co2 at best.

However my drop checker is a yellow/green colour using 4dkh solution accurate to 0.01ppm.

This would indicate 30-35ppm co2 and further more my aquarium water degassed is 8.3ph so I am getting a whole 1 point drop in ph which is about right for 30ppm co2.


Problem with relationship chart is it does not account for any buffers in water for KH or phosphate and this is even more apparent when you are EI dosing and adding 2-3ppm P04 on a weekly basis.