What is the best way to deep clean a tank?

[gordonuk]

I bought 6 18x12x12 tanks from gumtree for £30 and an extra £10 for delivery which I did not mind.
Anyway I knew the tanks were pretty grubby but a good clean and they will be fine.
I have mixed a bucket of bleech, all purpose cleaner and vinager together and will clean the much off with that and then once done will pop a few baby seterlising tabs in and get rid of any addital muck and germs.

is this the best way top do it for the tanks I have or is there a better way?

here are pics of the tanks as shown on the ad, to be honest they were a bit dirtier when they arrived as they obviously been stored for a while

[gordonuk]

also why do shops give you such a hard time when asking for sterlising tabs, they started going on about safety and how many to use and when i said it was a fish tank they looked horrified that i would do such a thing and then told me its not designed for that and its for babies bottles.
I felt like a kid walking into the chemist in the 1970s wanting condoms and coming out with a tube of tuthpaste.
They failed to realise certain products have alternative uses.

[superdart]

I use a lot of Citric Acid to remove lime scale and calcium deposits on my marine equipment.I get the crystals and mix it with RO water to my desired strength and soak until clean.I also use Stanley knife blades to scrape dried on crud off and scotch bright pads,water and elbow grease for the rest......have fun..
You say you bought 6 tanks but I think I can see 13 in your pic..

[gordonuk]

[superdart]

Ahhh 6 from the 13 ...I see.