Will I be able to see white "film" on fish tank when full of water?

Question

We were given a fish tank and it has a white film all over it. Lime maybe? I've been trying to clean it with vinegar, but it's not doing much good. When the tank is wet, it seems to "disappear". So I'm wondering if it will be visible when the tank is full of water.

Thanks!

Hmmm. The former owner had an Oscar (a cichlid). I have let it soak in vinegar and scrubbed it with salt (I smell like a potato chip). I believe it is etched. The worst damage is at the top and about 3-4 inches down. I think he didn't take the tank down right away after the fish died and this is where the water evaporated. The plastic on the hood and light are covered in white too. I really hope I can get that looking better.

Answer 1

If the vinegar won't remove it, then it's not lime you're dealing with. Chances are the tank was used in a high pH situation - for cichlids or saltwater, or your area has a naturally high pH. When exposed to high pH for a long time, glass becomes permanently etched. This can only be removed by flame-posishing - essentially remelting the surface of the glass to remove the small pits that cause the cloudy look. This is risky at best and there's a good possibility of the glass cracking, even it the work is done by a professional.

It may still be visible when the tank is filled, but it won't look nearly as bad as it does when the tank's dry. My suggestion would be to fill it to see what side has the least amount of damage, and if necessary turn the tank around (empty it first!) so the best side faces outward.

ADDITION: in response to your edit: Since most of the damage is at the top of the tank, it sounds like the previous owner also didn't top off for evaporations on a regular basis. Keeping ciclids, especially if they kept them at a raised pH, would be enough to etch the tank permanently.

Answer 2

i have that stuff. you will only be able to see it in the dry spots unless it is really thick. make sure you rinse that vinnegar out really well. try using aquarium salt. get a damp cloth and scrub the hell out of it. you can also get a NEW metal mudding knife and try to scrape it off.