Another vote for muriatic acid. I don't bother with vinegar at all. IMO - vinegar is too weak. Diluted muriatic acid does miracle. When cleaning my 120G and equipment, I diluted 1 gallon of acid in 120 gallon of water. Let it soak for a few days, and then just rinsed it really well. When I am in a rush, I'll use a 1:3 of muratic acid to water ratio. Quick and simple.
As pointed out, muartic acid does sink when poured into water, so make sure it mixes well. Usually, I will add water, some acid, and then some more water. If I am mixing a lot of equipment, I will toss in a powerhead to mix the water for me. Also -if you splash acid on you, rinse it off well with water. It may irritate you, but it won't cause long term damage. Also - wear eye protection or be very cafeful not to splash when pouring. Last - don't sniff the fume.