hey, i want to upgrade my lighting (currently just have the standard 18w juwel lighting unit in an 80l/20g tank)...Looking at the interpet compact t5 but really dont know what to go with. Id like to go from my currently 1wpg to around 2/2.5WPG but i have no idea how large the tubes are Realisticly ill be looking at a 24 watt unit, anyone know how long these tubes are? All the info you can give will really help