RDS Below Deck 18 Gallon Fuel Tank Special Order - Ships When Available. Contact customer service for more information on Special Order items. RDS has been a leading provider of custom aluminum fuel tanks for over 50 years. They are committed to the highest standards. The RDS Fuel Tank is a permanent below deck fuel tank that has been manufactured and tested to US Coast Guard and NMMA standards. Each RDS Fuel Tank is custom-made with 5052 aluminum alloy and 100 pressure tested to ensure it can w