new to salt few questions.

[Taboojen]

im seriously concidering setting up my 55 as a sw so i can have more fish and lr. i think i might set up a 20l as a starter tho.

The larger the volume, the more the water tends to stay stable (or more stable at least) - (ex: temp, ph, salinity, etc.) Especially if you are a beginner in saltwater, the larger the volume, the more forgiving it is when it comes to the occasional forgotten water changes and general husbandry of the tank. Corals and marine life tend to be less tolerant of change in their environment, so stability is the key. Thus, your 55 gal would probably be easier to keep stable, as you are almost tripling the volume of the 20 gal. Plus, when you want to add that extra fish you see at the LFS, then you can do so in confidence that you are not overstocking if you ended up using your 20 gal. lol. Just my two cents.

I'd go with the largest tank that you can afford/support, as you'll run into less problems in the long run.