The price of a canister filter may only be a few dollars more than a hang on type. The canister filter also allows more space for filter media to improve biological activity and water quality. Check the salinity the next day and either add more salt or remove some water and add some tap water. Leave the tank undisturbed for 48 hours after the final salinity adjustment before adding any organisms. The temperature of the water should, like the salinity, be as close to the natural temperature as possible.
Room temperature is fine, no heat is required.
There are 2 common soil bacteria, Nitrosomonas and Nitrobacter , that can convert toxic waste products from animals into non-toxic forms. These 2 genera of bacteria perform the same function in both freshwater and marine ecosystems. The chemical process is known as nitrification. Since this process is aerobic, good water flow and high dissolved oxygen levels will allow the process to proceed at a higher rate. Nitrosomonas converts ammonia, the initial and most toxic waste product, into nitrite.