Do You Really Need an Reverse Osmosis De-Ionization Filtration System(RODI)? By Lev Ingman
RODI stands for Reverse Osmosis De-Ionization filtration system. The main purpose of this filter is to remove harmful heavy metals, nutrients, organic wastes, and other disolved solids, that can have a negative effect on your fish tank, from your tap water. The water that comes out of the tap can contain harmful substances. In most cases many of these substances can be easily removed by simply using a cheap water conditioner. If you have a salt-water tank that does not have any invertebrates or a freshwater tank that does not have plants, then in most cases you will be perfectly fine using conditioned tap water and you do not need a RODI system. If you have a salt-water tank with invertebrates or a fresh water tank with plants then you probably need to get an RODI system. Some people will say, “Can I just go to the RODI unit outside my local grocery store, or at a specialty water store and buy filtered water?” The problem is that most of these places do not change their filters enough to purify water to the level that is necessary for some tanks. The simplest way to tell is to check the Total Disolved Solids(TDS) in the water that comes out of their machine. If the TDS is detectable then their filters need to be changed, but on my RODI I usually think below 10 ppm is acceptable. Even if the water that comes out of the filters is perfectly fine now, this does not mean that you can always trust it because next time you show up the cartridges may have become overused. If the filters were in fact recently changed, the water will be perfect now, but it is still not likely that they will be changed before the quality of water begins to decline. The same is true for fish stores that sell RODI water. Check it regularly and make sure what you are getting is quality purified water. If you have an expensive reef tank or a planted tank, invest the money get an RODI unit with a TDS meter to check it.