How do I clean old dirty tank?

[2xtheman]

I have a 20g tall tank and I want to relocate my 10g into the 20g. The 20g has been sitting in a garage with all the gravel and junk in the bottom for about 2 years. What should I do to make sure it's cleaned out properly before I use it? Also, should I just put my fish in a holding tank, and basically transplant all the water, gravel, decor into the new tank and add water before it put my fish back in?

Please no guesses, I want to do it right the first time!
Thx

[Northernguy]

Clean all your gravel completely or as good as you can with just hot water.
Clean out the tank with water and bleach.Rinse until there is no bleach odor and rinse again.Clean out your filter with just hot water.Put it all back together and start to cycle.Use what you can off your other tanks.

[bushwhacker]

i normally just replace any used gravel, been doing sand in my tanks now. as for the tank itself i set it outside pour in a little water and take a sponge and a box of salt and scrub the h*** out of it then rinse and rinse and rinse again same for the filter

[Lady Hobbs]

Straight vinegar will clean the tank of old mineral scale.

[wolf_eyes]

you may also want to fill it up completely with water outside and keep it filled for a day to make sure no leaks have developed since its been in storage. As for cleaning it, do what the others have said.

[KINGMED]

I would personally replace the gravel with other gravel or pool filter sand, I've rinsed my tanks out with salt (no iodine), vinegar and bleach--not sure what's the best, salt seems to be the cheapest and will kill most things I figure. If you clean with bleach I usually will clean with aprox. 1 to 2 parts bleach and 8 to 9 parts water, sometimes I use more bleach, after soaking and cleaning I will rinse the tank 3-4 times to get it nice and clean and then put about double or even triple the amount of declorinator in the water and fill the tank all the way up and let the bleach declorinate and then if I have time set it out side to air dry the rest of the way. I'm sure that's way to much but for me my money and time are very valuable and I would hate to kill my fish for not taking a few more minutes or an hour to do it right and loose all my fish and the money I spent on them.

[2xtheman]

keep it filled for a day to make sure no leaks have developed since its been in storage.

Thanks Wolf! Thats something I wouldn't have thought of.

I think I will use a bleach/water solution, just to ensure no outside bugs/molds are left before cycling.

Would the Penguin 100 I'm using for my 10g be large enough for sufficient filtration in a 20g tank? Whats the rule of thumb for water cycling rates?
tank volume/hour? tank volume/15min?

[Mvjnz]

If it's just been sitting there I wouldn't bother disinfecting it, I'd just give it a good rinse with the hose and then check it for leaks.

Fish come from outside, and they rarely live in sterile environments, so 'outside bugs' isn't a problem.

I bought 2 second hand tanks recently and only hosed them off and they've been fine. My pond is heaps filthier than any tank kept inside could ever be.