Auto Top off for Beginners.....


Manhattan Reefs
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Howell, NJ
hey guys since im no expert in any areas of marine aquariums, this is one thing i and many other newbies here need to make our lifes alot easier...

i want this thread to be full with pictures and how to do a auto top off.. anyone have any easy ideas.. and what is needed to do it...

thanks all.......


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I use products from

there are two float valves in my sump mounted on top of each other.

the bottom one electronically activates two solenoid valves to open and let in RO/DI water when the water level in the sump drops a small amount.

the top float valve is a back up, in case the bottom one is stuck/breaks the top valve will shut off the solenoids preventing a flood.

the solenoids are electronic valves that are closed in the off position, when they are activated they open and will only stay open as long as they are receiving the signal from the float switch. I use two as a backup.

they are connected directly to my RO/DI filter. If the valves were to both get stuck in the open position (something that would be near impossible) the RO/DI filter would continually pump fresh water into the sump.

Redundancy is extremely important for the way my auto topoff is set up.

I would not trade this feature for anything. It keeps the salinity of my tank exact, I never have to make RO/DI water for top off, and I do not have a large reservoir sitting next to the tank in my apartment. water is stored in a 4 gallon pressurized tank under the sink.


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Manhattan Reefs
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I'm using the Tunze osmolator that I got from StingNYC (Thanks Steve) and it works great and easy to set up.