cleaning tank

Question
what should i use to clean my freshwater tank with. All my fish died(9) in a 75 litre tank after 1 month.
The Tank started to go green and the fish all got like a layer of oil and cloudy spots. I conditioned the water and boiled everything when i set it up 1 month ago

Answer
At this point I would probably use a watered down bleach solution to clean the tank. It is safe to use so long as you do it correctly.  Scrub out the inside with a clean stiff brush and a watered down bleach solution as I said.  Scrub it down real well. Then what need to do is rinse rinse rinse and rinse again.  After you feel you have it rinsed out real well, re-fill it and use a dechlorinator double strength and leave it sit for a day. Empty that out the following day. Rinse again and then place your tank where it's going to be and fill it up again using normal strength dechlorinator (I like a product called "Prime").  I'm going to give you a link to read up on how to properly "cycle" a tank prior to putting fish in it. This is an important step that you must take prior to adding fish to your tank or it might wind up happening again.

You have to make sure that you don't use any harsh chemicals or oily chemicals on anything that you put in your tank.  You should use things designed specifically for fish tanks. I'm not sure what you had in there that might have caused the layer of oil, but perhaps someone used a chemical on or around the tank that infiltrated the water and poisoned the fish. It's important to not even use air spray in a room where a fish tank is.  Anything in an aerosol can can potentially get in to tank water because it is airborne.  But again, I cannot say for sure because I am not at your home, nor did I see the tank.

Here is the site I was speaking about:  http://www.americanaquariumproducts.com/Nitrogen_Cycle.html  This particular article is on cycling a tank, however, the whole site is full of great information.  I also invite you to join a forum which is just getting off the ground at: http://groups.msn.com/EverythingAquatic/  It's a great site to ask any questions like this and have them answered quickly. I am an assistant manager there, and we are looking for people to come join us and be involved in learning.

I hope this helps answer your questions. If I can elaborate on anything or if you have any other questions, please write me back or visit me in the forum, we'd love to see you there. I'm under the name "MrsCrabs".

Good luck!!   ;o)