55gal issue

Question
I received a 55gal and stand about 6 months ago.I said to myself cool a free 55.But now the question is that it has this type of what I call smoke screen haze inside.This haze is at the lower side of the glass panel and stretches all the way across the tank.Petsmart techs told me to use lemon and vinegar (which I already knew to try) and did nothing.Straight razor and panel scrubber did nothing either.I was wondering if you would know something about this issue or what this is.Also I heard on some other site about something called "etching" but I have no idea what that is or means.Your help would be greatly appreciated.[Tank has cycled and my current friends are 6 Tiger Barbs, 2 Red Wags, 2 of some kind of Molly(Wifes fish), 4 Blacktip Sharks, and a Pleco.Was also wondering if these guys are compatible together.Thanks, Jerry

Answer
Hi Jerry

It really depends on what type of tank this was prior to you taking it. If it was a salt water tank, there may be nothing you can do to clean it. If it was a freshwater tank, this is likely dried algae or water residue left over from improper maintenance by the previous owner.

Since you already have the tank up and running, the only thing you can do is hope the water softens this residue over time and it will come off using an aquarium scrubber. With fish in the tank, there are no chemicals (not even lemon) you can use that won't harm the fish.

Hope this helps, good luck!

Richard