Tom Aqualifter. Whatever you use, it has to be a pretty small pump. Otherwise it does stupid stuff.

I'm using a Rio 600 and its too big. Had to add a ball valve on the output of the hose.

I've got the hydor as well, and my only complaint is the overflow sensor is to close to the off sensor. I had a hard time getting it to fill without turning the alarm on. The pump that was recommended was way to small. It had a hard time pumping the water only a few feet, and was also affected by the water level in my reservoir. It pumped to much water when the reservior was full, and struggled to pump anything when it was less then half. I would recommend a dosing pump, or diaphragm pump. I ended up buying a innovative marine hYdrofill ato pump. It's quiet and works flawlessly.

Here is a pic of the ATO in action. The minimum run time is 20 seconds so I've had to slow the pump action with a TLF 1/2" ball valve, as I mentioned.
If it fills too fast the water level will rise and alarm will sound (annoying), not to mention messing up your salinity.
I have also noticed that the sensor needs to be cleaned of salt creep once a week. I use a Q-Tip.
Overall it seems like a good system, so far.

https://farm8.staticflickr.com/7366/...ca8050c8_z.jpg

Well I decided I would get the hydor and give it a try along with a eheim compact 300. Should have it by next weekend lol. Thanks for the advice and the tips.

Let me know how you like the Hydor.. I was going to buy that one then ended up making my own DIY Arduino Auto top off with optical sensor Its a similair idea to Tunze Osmolator Universal 3155

$40 aquahub DIY ato from BRS and any little pump $15-20 is what I use works perfect.

Plumbed directly into my RO unit, never needs filling :)

That's a nice feature. I was going to automate water changes but I'm setting up the new tank in the living room. It would be along way to fish wires Defiantly a nice way to go though!

I went through a wall and used some baseboard conduit. Haven't topped up my tank in 5 years.