Good Water or Bad Water

Hello Everyone,
I don't know if any of you going through where you have your water sitting in an empty tank for over a year with out any heat or water flow. I'm having my tank almost full of water for a year now and would like to know if the water is still good. I have noticed its kind of dirty with a thin layer on top and offcouse they should be drained out.... My question is do I have to drain the whole tank or just part of it.... Thank you in advance for your suggestions.

why even think about using it? i would drain the whole tank then srub the tank clean then start entirely with new water. you never know what kind of stuff got in there after a year of sitting...

Thank you! I was being lazy I guess ....Kind of hoping that I have to drain just part of it... too busy with other projects that's why I don't have any fish in there and been sitting for over a year, plus it's about 500 gal of water and will take hours to drain...and the cleaning on top of that ...hope I will have sometimes this coming holidays to get some work done and might thinking of getting some fish to start out in the late Summer...

Thats just nasty! Clean it!

i would not even think about using it

Go to home depot or ace and buy the biggest flexible tubing that they have a 2"-3" should help drain it a hell of alot faster... I bought a 1" to drain my 100 because 1/2" took to long for me... I am impatient when it comes to draining tanks

Thank you guys for all your suggestions. It'll be my project for this coming holidays.... I just tried to open the lid and see how bad it is and it was smell kind of - well you know...not a good thing ........ hope my family will not try to convince me for a long road trip to Portland this weekend....

stale water that sits like that is a crazy breeding ground for harmful bacterias... definetly not usable.... I wouldnt even trust the decor... now if you had a filter circulating the water constantly, that might be a different story.... but stale water with no air passing thru it, bad stuff... good luck.

Get a pump or a large diameter siphon to speed things up.do not use the water with fish....maybe with carp.