The reason we suggest a larger size tank is because its proven that larger size tanks have more stable water conditions. A 55 gal
tank will be much more stable than a 10 gal
tank for example.
The reason is there is over 5X the volume of water. Water temperature rises slower, ammonia levels increase slower, etc. There are many conditions to monitor on saltwater like temperature, salinity, ammonia, alkinity, nitrite, nitrate, PH just to name a few.
We are not saying you CANT do a 20 or 10 or even smaller tank to start out with but what we are saying is that you WILL have to monitor your tank alot more than if you started out with a larger tank.
For example in saltwater tanks when water evaporates it leaves the salt behind. Thus as the water level i nthe tank lowers the salinity increases. To bring water levels back up we add freshwater to the system to replace wat is lost. Failing to maintain proper top off schedule on a small system can cause your SG
levels to fluxuate greatly leading to stress on the fish and corals inside the system.
Also a common problem with any one new to saltwater is overstocking the tank. Saltwater fish are naturally more agressive and take more room per fish than freshwater. This is partially because their natural habata includes the largest body of water known to man. There is also less oxygen content in saltwater. Going with a small tank is really going to limit your fish selection and quantity of fish greatly. For example one of my saltwater tanks is 20 gal
and it has 1 maroon clown in it. If I added any other fish they would surly be killed before sunset. This guy attacks your hand when its in the tank.