I was never happy with my Dwyer flow meters. The first one I purchased was used, it was inconsistent, and while adjusting the flow the float would jump around. So, I splurged and purchased a new one, but for the flow I needed it registered a low reading that was not helpful. So I learned to adjust CO2 based on the plants(as much CO2 as possible) and fish(as much CO2 as possible before it really affects them). Really this approach is how it should be done, as numbers are just numbers, the important part is how the fish and plants react.
But I’m an engineer and I like building items and making them way to complex. Heck, that half the fun of this hobby! So when @Bettatail
posted about the Porter FM, I jumped on the bandwagon and purchased two flowmeters! I like the Porter FM quite a bit more than the Dwyer FM. The Porter FM has a scale length of 6.5 inches long, whereas the Dwyer FM has a scale length of only 2 inches. Plus the valve is much smoother that either of the two Dwyer FMs I own.
Not content with just hooking it up, I decided it’d be fun to add pressure gauges on the incoming and outgoing lines. Of course, I’d have to have an appropriate mounting panel. I used a piece of 1” x 4” premium pine to mount the gauges and flow meter, drilled the appropriate holes, painted it black and attached the items. For mounting the gauges and flow meters I used Velcro. I find Velcro easy to use, plus it allows fast access for removing and adjusting equipment. I also used Velcro to attach the 1”x4” mounting panel to the aquarium stand.
Ideally I should be able to take the outgoing pressure and knowing the flow I should be able calculate the actual flow of CO2 with respect to Standard Temperature and Pressure(70į F at 14.7 psi atmospheric pressure)(STP). The reality is the accuracy of the gauges and flow meters are fair, plus temperature of the gas has an affect on flow rates. A better way of determining actual flow is measuring the weight of CO2 used by weighing one’s tank over a period of time and calculating the amount of CO2 used at STP. One can calculate the volume of CO2 at STP manually or use an online calculator such as the Air Products calculator
After coming up with various ways of using a fish scale to determine the CO2 tank weight, I figured it was going to cost about $20 to $30 to implement. But then I thought why not do a search on Amazon and if I could find a accurate floor scale to accomplish this. Fortunately, I found one for less that $35, the Smart Weigh Digital Shipping and Postal Scale
, 110lbs x 0.1oz. It’s nice unit, and seems to be working fine. The floor scale works out much nicer that looking at the low-pressure port pressure gauge and trying to guess when my tank will be empty. Since I know my tank weighs 20lbs-1oz pounds when empty with the regulator attached, if I know what the daily consumption is, I should know within a day or two when my tank will run out of gas.
The interesting part about measuring CO2 is I don’t see where there’s a standard in the planted tank community regarding the measurement of CO2. I’ve only seen bubbles per second or CC/Min. Both of these really can’t be used as there’s no accuracy because the size of bubbles is dependent on pressure and temperature. The same applies towards using CC/Min; most folks are just reading what’s on the scale and not adjusting appropriately for temperature and pressure. I’m thinking grams/hour or grams/day may be more appropriate. Anyone have thoughts on the item?
The following are photos of the installation.
The backside of the panel with tubing connected.
Mounted within the aquarium stand:
CO2 tank with Scale:
Closeup of Scale: