Water changes and Kalwasser

drud0616 · Sep 29, 2014

Hello all, just wondering if all of you are doing scheduled water changes regardless whether the water chemistry is off or not.
I'm running a 55 gal tank with protein skimmer, cannister filter, some SPS and fish and have not done a water change in about 3-4 weeks now. I have been checking my salinity(via refractometer), pH, ammonia, nitrites, nitrates and they are all within the required parameters.
I've been dripping Kalwasser and checking alk, Ca, and Mg with pretty good results. My main question is...why do scheduled water changes if the parameters are within normal limits?

Tamberav · Sep 30, 2014

I do it because there is a lot more to it then ALK/Ca/Mg in reef salt. What about all the trace elements you can't test for? I figure they play some role in a healthy tank.

I have a supplement with trace elements but not sure if it covers them all so I just use it between changes.

Randy Holmes-Farley · Sep 30, 2014

It is fine to experiment with running a tank without water changes. A reasonable number of people do it.

In general, however, I think that water changes are useful for a variety of reasons, which are described below from one of my articles:

Water changes are a good way to help control certain processes that serve to drive reef aquarium water away from its starting purity. Some things build up in certain situations (organics, certain metals, sodium, chloride, nitrate, phosphate, sulfate, etc.), and some things become depleted (calcium, magnesium, alkalinity, strontium, silica, etc.). Water changes can serve to help correct these imbalances, and in some cases may be the best way to deal with them. Water changes of 15-30% per month (whether carried out once a month, daily or continuously) have been shown in the graphs above to be useful in moderating the drift of these different seawater components from starting levels. For most reef aquaria, I recommend such changes as good aquarium husbandry. In general, the more the better, if carried out appropriately, and if the new salt water is of appropriate quality.

Calcium and alkalinity, being rapidly depleted in most reef aquaria, are not well controlled in most established aquaria, or even significantly impacted by such small water changes. In order to maintain them with no other supplements, changes on the order of 30-50% PER DAY would be required. Nevertheless, that option may still be a good choice for very small aquaria, especially if the changes are slow and automatic. Also, some mixes have very high levels of calcium in them, and these may be able to maintain calcium in aquaria that have relatively low demand for calcium and alkalinity.