ADA · Regulator
PS-SC Speed Controller
Keepers running pressurised CO2 who want finer adjustment than their regulator gives, or split lines to two tanks.

UNS · Regulator
The add-on solenoid for the Micro regulator. Plug it into a timer and your CO2 switches on and off with the lights instead of running all night.
Updated
Anyone already running the Micro regulator who wants CO2 on a schedule.
It only fits the Micro regulator; the Mini and Pro regulators already have a solenoid built in.
Figures from Glass Aqua's product listing. Makers revise products, so check the current figures before buying. Photos supplied by the brand or its distributor.
ADA · Regulator
Keepers running pressurised CO2 who want finer adjustment than their regulator gives, or split lines to two tanks.
UNS · Regulator
Desktop nanos where every centimetre of space around the tank counts.
UNS · Regulator
Nano and small tanks, especially if you might switch from cartridges to a refillable cylinder later.
UNS · Regulator
Medium to large planted tanks and fish rooms running refillable cylinders.
Quick answers about the UNS Micro CO2 Solenoid, drawn from its specs.
Anyone already running the Micro regulator who wants CO2 on a schedule.
It only fits the Micro regulator; the Mini and Pro regulators already have a solenoid built in.
Other co2 worth comparing: ADA PS-SC Speed Controller, UNS Micro CO2 Regulator, UNS Mini CO2 Dual Stage Regulator. Add any of them to the compare table to see the specs side by side.
Tap Compare on this page and on any other CO2 product you are considering, then open the compare table. It lines up every published spec side by side and lets you pick the size of each product.