considering buying a controller or tunze osmolator

[rich850]

i already have an auto top off but sometimes i have some problems with it overfilling slightly which lowers salinity in my tank i am just curious how an apex or reefkeeper controls auto top off does it pump a certain amount in daily or does it have a sensor for salinity and when it rises it kicks on the auto top off pump ??? i just dont completely understand how the apex and reefkeeper controllers work i have been looking on bulk reef supply at them and everything is very vague if anyone could help me out with some detailed explanations i would greatly appreciate it

 

[SaltyMember]

For the price of a tunze top off you are almost at controller prices. I have a reefkeeper lite and how it works for topoff is you plug float valves in to the unit. I have two I'm my sump. One controls my top off pump and adds water when my water level drops. The other is a backup that turns off my pump if the first float switch fails or gets stuck. Digital Aquatics actually sells float switch kits that make the process very easy. You can do the same thing with the Apex controller also.

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[moonpod]

As noted above, aquarium controllers use float switches. There are controllers that also use salinity probes, but I dunno specifically if the RK or Apex have that option. That makes things really complicated however. Generally if you top off with fresh water to the same level in the sump, your salinity won't vary much. The tunze uses an infra red "eye" instead of a float. IME dead reliable super accurate, but it's not like float switches are terrible. The osmolator (at least used to) also comes with a pump, tubing etc..., but yeah, it's pricey because you are using an eye instead of floats. It also has a float as the backup/overfill switch kill. You can go either way. There are pros and cons. floats are cheaper, the eye probably more reliable. Depends probably on just how paranoid you are and how far you need your dollar to stretch.