Some beginner questions...

[Be102]

I recently added a sump, Ive yet to water change since the sump addition. I was curious what everyone recommended was the best way to do waterchanges with a sump. From the sump? From the display with the pumps off?

Also, I was wondering how I could go about creating some sort of float switch for my ato. Currently I have it hooked up to my sink and if I forget about the bucket long enough I tend to start to overflow. Any ideas?

 

[Fudsey]

I do every other water change from my sump cleaning from the bottom with the hose. The other I do from my tank and sump, vacuum the sand and clean the sump.

My ATO is me, as I don't trust ATOs at all. Too many horror stories of over flowing and killing inhabitants of tank. I add a gallon of water per day

 

[Mjp83]

I turn of my return pump, which dumps about 20 gal of water in my sump. I leave my powerheads on to keep water moving in the display tank. I also vacuum out the sump and clean the skimmer, heater and return pump. I do a thorough clean of equipment every other water change or so.

Once sump is clean I fill it up with new water, and at this time I skim off the remaining water from the display, to make up the total water change. I have a 125, so I do about 30 gal. About the time I am done pulling water out, I turn my return back on, and it pumps the water back in the main tank, as the new water fills the sump.
I have the ATO brand ato, and it works very well. To be honest, keeping everything at a constant level in a reef is the true key to success, and that includes salinity. The ATO will cover that. I too added too much water and let it get way low before the ato! Now I have dosing pumps as well and my tank is doing great!

 

[Radman73]

It's up to you. I generally have done mine from the display tank but occasionally from the sump. I've also had auto water changes configured and will likely do that again. If your sump is dirty, siphon out the detritus or do your water change there.

There's no hard rule on how to do water changes so find a routine that works for you and that you'll do.