If I dont feed the tangs plenty of veggies they quickly begin to nibble on ALL my corals.
I doubt that would happen. But first, I would like to point out a statement about tang dietry. Lettuce, cucumbers, Broccoli, etc., are not good for saltwater fish. These human foods are very difficult for tangs to digest, and will result in long term damage. It is true that tangs do need a fair amount of herbavorous foods, but this means natural foods, such as Nori (unroasted, unsalted), algae, etc. Lettuce and other human foods is not a part of the tangs diet and should not be fed to any saltwater fish.
Also, tangs usually do not nibble on coral if they're hungry. Unless you have seen the tang directly come up to a coral and take a bite out of it, then we have another discussion.
Second, I doubt your nitrate problem is from the vegitables. You stated "tangs" in your post, meaning you have more than one tang? What size tank is this? How many fish are in that tank? What filtration do you have? How much do you feed? How deep is your sandbed, and what's the substrate?
Graham
