hi steve!
short comings... hmmm...
i would redo the hard pvc with flex pvc so to make it nice and compact,
i would mount a probe bulk head on top for a PH probe and monitor with a controller
i would control the co2 solenoid via this controller as well
i am not sure why, but some of the co2 microbubbles collects up under the lid, it could be better if the lid funnel these bubble towards the flow inlet, i end up shimming it, giving it a slight lean towards the effullent output and the extra co2 comes out that way,
when i first got it online, the bubble counter thread and pump thread had a very slow leak, i ended up redoing it with more teflon tap..
the acrylic work is not like a Vertex Alpha by Royal Exclusiv...
dialing in for the reactor ph is easy... i used to put the effulent drip into a cup and put the PH probe there...
dialing in for your tank... I bet that be easy for you too
