There are alot more experienced people to chime in here, but to make it easier, you will need to give ALOT more information. Such as, why only 30 gallons in a 55? What is your main goal for this tank? What are you stocking (fish, livestock)? If for fish, how many? What kind? What substrate do you have? What lighting are you going to use? Are you using CO2? What is your experience level? You see where I'm going with this.. This Forum has so many "Aquatic Geniuses" . The more info you can give, the better they can GLADLY guide you, just as they have done for me time and time again! BELIEVE ME you're in the best place for guideance! Good Luck with your project!