Yep, a popular water treatment is called Seachem Prime. It's extremely concentrated so it lasts forever. The bottle is more expensive than other brands but it will last you longer so works out cheaper. You'll probably want to get a syringe for dosing it. I use a 5ml syringe to dose my 180L tank and that's more than enough.
As for emptying your tank. Where is it? I've got a "no-buckets" python system that I made myself. It cost me about £35 to get all of the parts for it but it's worth it in my opinion. If you don't want to go that route then a big bucket and a gravel cleaner/syphon kit is all you need (just make sure it comes with a long enough hose for you)! Even if you do decide to make a no-buckets system you should still have a gravel cleaner as you will find you occasionally still need it.
I'll try and find the link to how to make it.