What you saw could have been just about anything, there are so many different kinds of dosing equipment for aquariums. Just a few.....
http://www.aquariumguys.com/dosing.html
Monitors, controllers, meters, dosing pumps, all kinds of stuff. It's come a long way from when you set a water bottle up on a shelf and dripped water in from it, or at best ran a tube from it to the Fill Line in the sump and water would be fed in whenever the level got so low that air could bubble up into the water bubble and displace the right amount of water.
http://www.aquariumguys.com/dosing.html
Monitors, controllers, meters, dosing pumps, all kinds of stuff. It's come a long way from when you set a water bottle up on a shelf and dripped water in from it, or at best ran a tube from it to the Fill Line in the sump and water would be fed in whenever the level got so low that air could bubble up into the water bubble and displace the right amount of water.
