tank tablet for rust/hard water

I have seen the advice against using those blue tablets in the tank. What about white tablets for treating rust/hard water stains? I saw some at my local Ace Hardware today.

Will I get "white goo" instead of "blue goo"?

I tell my customers not to put ANYTHING in the tank

especially "2000 flushes"... you can smell the chlorine from those things when you take the lid off

I have heard that putting anything in a toilet tank can eventually cause problems with internal plastic parts, but my wife found this stuff somewhere and we have had no problems over the past two years we have been using it. However, it disappears too quickly if you just drop it in the tank, and it once got pulled into our flush valve and blocked it open. So, I now use its packaging blister like a cup to contain it and to let it dissolve more slowly, and I put a large (3/4") washer on top to hold it in place in the corner of the tank. And yes, at least for us, it essentially eliminates rust stains in our bowl and tank. Interestingly, however, that washer is beginning to corrode ...

I've always put all that goop onto the "crap" category. Just something to get your money.....