Is this rust in my fish tank?

I have a five gallon tank in storage that seems to have what looks like rust on the bottom. It won't come off no matter how long and hard I scrub. I don't know if it's actually rust as glass doesn't tend to rust but I have no clue what else it could be. I did have an alcohol thermometer break in there, not sure if that could cause it. Had a few river rocks in there as well and they seem to have this rust looking stuff on them as well. I've tried cleaning it with white vinegar, it didn't work. I have no idea what it is or how to get rid of it, but my main question is, is it safe for fish? I don't really care about apperance, I'd just like to be able to use the tank. (No cracks in tank there's just hay underneath)

 

No idea what it is. I would put water in it for a day then do testing as long as water parameters are fine I'd use it

 

No idea what it is. I would put water in it for a day then do testing as long as water parameters are fine I'd use it

Ok thanks. I'll probably set it up soon. Say it is rust and it's somehow stuck to the glass, is it safe to use the tank with that much rust in it?

 

As long as water tests close to what it is from tap I wouldn't worry. If tests are off I'd assume something leeching into water and buy new tank not worth taking a chance.

 

Thanks for your help! I'll just test it and see

 

I doubt it is rust. Could be diatoms.

 

Could it be mineral leech from the rocks ?

 

Try scraping with a razor. This would be the easiest IMO.
Looks like iron staining.
Many rocks leach iron.
5 Ways to Remove Iron Stains - wikiHow
I do not think it is a threat so if it doesn't come off don't sweat it.

 

Thanks for the help guys! I'll try to get it off with a razor blade.

 

Maybe try CLR? That stuff seems to get off anything. Just rinse it well. Or Barkeepers Friend?

 

I soaked it in vinegar overnight. The patches are still there but not as bad. The vinegar is all brown now so it must've done something. Its a little hard to see in the picture.

 

Since its on the bottom maybe try a SOS pad or some kind of scrubber pad?

 

Just finished scraping it off with a razor blade, got rid of most of it. I decided to give the whole tank a deep clean in the process and it looks amazing! I'll show some before and after pictures. Thanks for all the help!

 

Ooh shiny now for the fun part of setting the tank up !

 

I know! I love setting up new tanks, I will have to wait a while though cause I don't have a heater or filter for it yet, but I should get them soon.

 

It is brand new