Blow off tube question

I'm using a Better Bottle (6 gal) for my primary now and just hooked up a blow-off tube.

My friend mentioned that I should have used sanitized water in the blow-off tube vessell because when fermentation starts a little water ends up getting sucked up but I used plain old tap water.

What do you guys generally use in your blow-off tube vesell?

I use a half-gallon growler filler with iodophor/water mixture. I've used plain water in the past as well with good results, but recently change to the iodophor mixture just to be on the safe side.

I've never had a problem with the blowoff sucking water back into the carboy, I can't even imagine how that would happen....

I use a small pitcher with about a quart of regular strength star san.

I typically use a plastic gallon jug (like what milk comes in) half full of iodophor solution (I just use what's left over from sanitizing my brew day equipment). Works very well.

I always put on an air lock first and fill it with star san. If there is any suction, I can rest easy know only star san is getting pulled in. After fermentation starts, if I think I am going to need a blow-off, I put one on into a jug with water (or star san if I have some old lying around). Since by that point there will be no suction there is little to worry about.

Well I just had it happen. I ferment in a temp controlled chest freezer. Fermentation was done so I crashed to 33f. I forgot about the half-gallon growler filled with just water as a blowoff. all was sucked back into the 2 batches which im hoping and assuming will be just fine so when you cold crash take off the airlock or blowoff.

I use a skinny pint bottle with about an inch of cheap vodka in the bottom.

I just use a half gallon jug with about an inch or so of water in the bottom. Never had any problems and can't imagine that any water would get sucked back into the fermenter. There is so much positive pressure in the carboy I don't see how it would happen.

After high krausen is done I'll switch out the blow off tube for an airlock.

Suck in happens when you cool the wort only enough to pitch, and not to room temp of where youre storing it. Also slow starting yeast will contribute because the longer they take to get active, the longer the wort has to cool and start this vacuum. The only real ways to eliminate this are to use a yeast starter to make sure the lil beasties are active when you pitch, cool your wort closer to room temp, or use a blowoff tube instead of an airlock (this will require a lot more force to suck up).