Filter Media Buyer's Guide
Understanding what different types of filter media do, and how they should be used in a reef aquarium can be a challenging task, especially if you have never used them in your tank. Here's a quick a simple buyer's guide for filter media to help you make an informed purchasing decision.
Aquarium water is loaded with impurities and heavy metals that are bad for your water quality. Carbon absorbs those impurities and tannins, keeps your water sparking clean and helps keep the foul fishy odor from taking over your house. Carbon is also used to remove medicated treatments from the water and keep the toxins secreted by corals out of the water.
Carbon works best in a fluidized media reactor with moderate water flow, or it can be used in a filter bag if placed in a high water flow area like an over flow or a sump. Carbon should be replaced every 3-4 weeks depending on the bio load of the tank. If you notice your water is dirty and smelly, change the carbon sooner.
GFO is used to remove phosphate and silicate from the water. Algae is fueled by phosphates, so using GFO on a regular basis is an effective way to keep phosphates and nuisance algae under control. GFO can affect your aquariums alkalinity, so be sure to test and monitor your alkalinity levels when using GFO. Also, GFO does not leach phosphate back into your water.
GFO works best in a very low flow media reactor. Too much water flow and the delicate nuggets can easily be broken down, resulting in a fine red dust covering everything in your tank. GFO should be replaced and replenished every 4-6 weeks, or as needed based on the phosphates present in your reef aquarium.
Bio pellets and synthetic resins are primarily used to control nitrates, however they can also absorb organic pollutants such as nitrite, silicate, phosphate, heavy metals and other impurities. Synthetic resins target specific impurities such as phosphate or nitrate, so be sure to select one that will work for your needs.
Bio pellets should be used in a media reactor with a rigorous and turbid water flow for best results. Other more delicate resins should be placed in a fine filter media mesh bag and placed in a high water flow area of your tank. Some synthetic resins such as Seachem Purigen can be regenerated making them very cost effective. Different resins expire at different rates, so be sure to follow the manufacturer's directions for usage and replacement schedule.
Using any filter media will have a direct affect on your water parameters, making it critical to test your water parameters on a weekly or sometimes daily basis depending on the water parameter being treated. For example, if you are employing GFO in a media reactor for the first time, you will want to closely monitor your phosphate and alkalinity levels until they stabilize. Make sure you use a good test kit that is intended for reef aquariums and that give highly accurate readings. Basic saltwater test kits often times do not have a high enough resolution to accurately monitor critical parameters.