
We all know how important it is to use only high quality water in our aquariums. Many of us use reverse osmosis filters or reverse osmosis filters with a final deionizing stage to provide us with the highest quality water possible. Unfortunately, we may be doing this all for naught if we aren't using our RO and RODI filters properly.
Most RO / RODI filter owners know what TDS is - and know that it is something they want to keep as low as possible. What some may not realize is that while the RO filter is working properly, the water they are adding to their aquariums on a daily basis may be little better than the tap water coming in from the municipal supply. How could this possibly be happening???
Every time an RO filter starts producing water after being shut off for any period of time, the initial output is of very low quality. Luckily it's likely devoid of chlorine thanks to the carbon filters, but it is very high in total dissolved solids (yep, "TDS") for the first couple minutes. After a few minutes the product water is as pure as it can be - but if the filter doesn't run for several minutes at a time the water quality is never as high as it could be. That's where the problem lies.
Many aquarists have the output of their RO filter hooked directly up to their sump with a mechanical float valve. Whenever the water level drops just a tiny bit due to evaporation, the RO filter dutifully produces just a little water and then shuts off. Often it produces water for just a ...
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