"restoring" change water in low stocked tank.. Possible?

[KonradTO]

Hi all,
Has anyone tried to treat (filtration, macro) the water from WC and re-use it for the next WC?
What downsides there could be?

 

[Randy Holmes-Farley]

The downside is the water will not be nearly as useful as new salt water. Water changes add and remove lots of dissolved substances that you will not be able to control by trying to treat it.

 

[Garf]

You could get a Refugium or Algae scrubber on your tank to do that job, but you’ll probably still end up doing water changes or at least dosing all sorts of elements.

 

[KonradTO]

Ok I see. My point was that with 10% WC if dosing it's necessary anyway you would just take in account how much Mg-Ca-Alk are depleted along time and just re-introduce those every now and then and for micro you could simply add them when needed. I guess the problem is that you don't know which elements are being used and which not right?

 

[Randy Holmes-Farley]

Ok I see. My point was that with 10% WC if dosing it's necessary anyway you would just take in account how much Mg-Ca-Alk are depleted along time and just re-introduce those every now and then and for micro you could simply add them when needed. I guess the problem is that you don't know which elements are being used and which not right?

These are my reasons for doing water changes, but not all do them at all:

Water Changes in Reef Aquaria by Randy Holmes-Farley - Reefkeeping.com

Conclusion
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, 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.

 

[KonradTO]

These are my reasons for doing water changes, but not all do them at all:

Water Changes in Reef Aquaria by Randy Holmes-Farley - Reefkeeping.com

Conclusion
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, 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.

Tanks for the link, very interesting. I might use water changes for a second tank with resistant species if I can convince my wife to get another glass wasting so much water every week really bothers me a lot, especially from the environmental point of view. I could run a brackish tank maybe..