Dropping CO2 pressure

• pH:
• Temp:
• KH:
• GH:
• NH4:
• NO2:
• NO3: 10-20
• PO4: 1.25
• Iron:
• Dosing: 5 mL Flourish, 0.5 ppm iron chelate
• NO3:PO4 Cumulative Dosing Ratio:

Notes:
The danio pair were jumping into the AquaClear filter, and this time, I could see some of their eggs pouring out of the filter output as they splashed around inside the filter. The other fish were happy to have a caviar snack.

I also noticed that the pressure of the CO2 tank has dropped. It usually hovers around 900 psi, but it's been steadily dropping over the past couple weeks, and it's now at around 600 psi. As the pressure drops, the low pressure gauge in the regulator has increased from about 20 psi to about 40 psi. I will probably go get it refilled tomorrow at a local welding supply store.

The pressure usually begins dropping after all the CO2 in liquid form has been used up, leaving only CO2 gas in the tank. Supposedly, there is a danger of the regulator/valve becoming unable to regulate the flow of gas when the pressure drops too low, causing the remaining CO2 to suddenly dump out of the tank all at once ("end of tank dump"), which the fish will definitely not appreciate. To be absolutely safe, you should get your tank refilled when you first notice the pressure dropping. Some people will wait till the gas drops to 400 psi or even lower, it depends on a person's love of risk.