No doubt it has phosphates, but I believe that adding a couple of ounces of it to a 120 gallon system will have a negligible affect. And besides thats why I run gfo and bio-pellets.

The cloudy water is full of phosphates. Run a test and put in a drop and you'll see how much there is. My color changed drastically and since then ive always rinsed

I've always always rinsed. Never dared to think about putting a cube in without rinsing! The stuff that runs out probably feeds the algae more than the corals.
I target feed my corals whatever I feed my fish.

Same method as others. Place the cube in a fine mesh and run tap water through it until water runs clear.

I'm surprised this many people don't rinse.

Good article on the subject by Randy Holmes Farley

http://www.advancedaquarist.com/2012/3/chemistry

I have some phosphate issues in my tank as it is, so I started rinsing in a small cup with some tank water. Couldn't hurt.

Don't do it.... packed with phosphates... be alright if you were growing algae... lol

Haha I just came on to put the same article up. Interesting read but I'd still rinse.

Yep I still rinse too lol

I currently thoroughly with tap water but I find that fish do not have that great of an urge to eat it as much compared to when I do not rince it.

"A half cup of water at 1 ppm (1 mg/L) phosphate contains a total of 0.12 mg of phosphate. A cube of Formula 2 contains about 11.2 mg of phosphate. So the hypothetical rinsing step has removed about 1 percent of the phosphate in that food. Not really worthwhile, in my opinion, but that decision is one every aquarist can make for themselves."

Thats the part that concretes it for me. I've never rinsed frozen food, simply because its effects are negligible and the phosphates are going to get in there anyway. Plus the feeding response from my corals is greater when the fine particles are left in the tank.

Granted, I prepare my own frozen food, but there is some mysis in there, and cyclop eeze, both of which go into the mix unrinsed. I have never had any algae issues as a result.