The best discount codes for SaltwaterAquarium.com are SALT10, SALT20, and SALT30. These codes offer $10 off orders $200 or more, $20 off orders $300 or more, and $30 off orders $500 or more respectively. Please note that these codes exclude products from MAP manufacturers such as Ecotech Marine, AI, Neptune Systems, Red Sea, Reef Octopus, etc. Each promo code can be used once per customer. Additionally, there is a 5% off deal for all brands for Military & Civil Servant. Free shipping is also offered on all orders over $39. Please remember that these codes and deals are subject to change and may have certain terms and conditions. It's recommended to check the official website for the most current and accurate information.