How long will a 2.5lb Co2 tank last in a 65 gal

[Fish Breath]

Hi! I had a friend give me a 2.5lb Co2 cylinder and was wondering if anyone could tell me how long it would last using it on a 65 gallon aquarium. Thanks in advance
F B

 

[malkore]

A day, a month, a year....

No real answer to this, because every tank uses a different amount of CO2 depending on tank size, % planted, types of plants, lighting, fish load, type of reactor/diffuser used, surface agitation...

The closest rough ball-park figure I could give you is 2months to 8months.

As a point of reference, I can get about 10 months out of a 5lb cylinder on my 75gallon tank, running 35ppm, 24 hours a day.

 

[workfortheman]

I've been reading up on these alot lately, and have heard many stories about 5/10 lb cylinders running out in a couple weeks due to leaky connections. If you find this happening they suggested applying soapy water to the connections and check for bubbles.

Malkore's advice is all good, and I would stress the importance of an efficient diffuser, as well as little surface agitation.