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I've been struggling to keep my salinity stable with my current ATO setup. It's a 75-gallon mixed reef with a Tunze Osmolator, but I'm seeing swings from 1.025 to 1.027. Anyone got tips to dial it in better?

What's your reservoir size? I've found that larger reservoirs (at least 5 gallons) help buffer against rapid swings. Also, check your ATO sensor placement—too close to flow can cause false triggers.

I had the same issue until I switched to a dual-sensor ATO. The redundancy cuts down on errors. Also, topping off with pre-mixed saltwater instead of RO helps if your evaporation rate's high.

frostlyn wrote: ↑Tue May 13, 2025 4:37 am I had the same issue until I switched to a dual-sensor ATO. The redundancy cuts down on errors. Also, topping off with pre-mixed saltwater instead of RO helps if your evaporation rate's high.

Yep, dual sensors are clutch. I run a 10-gallon reservoir with a float switch and optical sensor, zero issues for 8 months now.

How often are you calibrating your refractometer? I've seen folks chase salinity ghosts only to find their tool was off. Use a 35ppt solution to verify.

My ATO's basic—just a float valve in a 3-gallon jug. Salinity stays at 1.026. Maybe your Tunze's overcomplicating things?

I'd check for leaks or kinks in your ATO line. Had a tiny drip once that threw everything outta whack. Also, what's your room temp? Big swings can mess with evaporation rates.

Thanks for the suggestions, everyone. Gonna test my refractometer first, then look into a bigger reservoir. Appreciate the help!

guppyfin wrote: ↑Tue May 13, 2025 10:43 am Thanks for the suggestions, everyone. Gonna test my refractometer first, then look into a bigger reservoir. Appreciate the help!

Smart move. Let us know how it goes. Oh, and keep your reservoir covered—dust can gunk up sensors over time.

One last thing—if you're dosing anything, make sure it's not near the ATO intake. Stray Kalk paste nearly bricked my sensor once. Sketchy stuff.