Can I stop doing water changes?

[stanleo]

I have been thinking that I could stop doing water changes. My Alk had gotten dangerously low so I figured out how to raise it and to keep it stable I started using an auto doser with four heads 5 days ago and dosing soda ash. The alk has been stable at 9 dkh ever since. I have been testing daily at the same time every day. My calcium and magnesium never budge, they have been 500 ppm and 1520 ppm for the better of a year, tested weekly. Before that they were actually higher. Neither does my PO4 and NO3. They are always 0.03 and 2 ppm.

My corals grow, I have montis, hammer, xenia, kenya tree, birdsnest, and a brain coral. I have anemones, an urchin, shrimps, crabs, and snails. There are 4 cardinals, yellow tang, clown, damsel, mandarin, watchman goby and a blenny, I don't have any mysterious die offs and the shrimps and crabs molt regularly. The only nuisance algae I have is turf algae and the diatoms on the sand bed are starting to go away since I stabilized my alkalinity. The corals I haven't had success with are zoas, acans, and a torch.

Since I started the tank over a year and a half ago, I have religiously done water changes of 20 gallons every two weeks. It is a 120 gallon with a 55 gallon DIY sump that includes a 20 gallon refugium with chaeto that I have to thin out every month. I actually just gave away a four gallon bucket of chaeto because I let it go for too long and it almost completely filled up the space. I run the protein skimmer constantly and empty it weekly. I have done water changes not for nutrient control but more for replacing trace elements I don't test for.

Now that I have my alk sorted out, my nutrient levels never rise, my calcium and magnesium are so high, and I have 3 auto pumps left on this doser I was wondering if I could stop water changes altogether or maybe reduce them to once a month. I would keep doing weekly water tests and if/when the calcium and magnesium drop, I could use the other pumps for dosing those elements. Or is this a bad idea altogether and I should just keep doing things the way I am doing them? I wanted to know if anyone on here had any thoughts on the subject.

My biggest concern and why I really want to know is I think my calcium and magnesium are too high for some animals that I want to keep, like clams. I would like these levels to drop and then keep them stable.

 

[Jdubyo]

You can stop doing water changes as long as you are testing and dosing for all of your other elements. You have the big three down (alkalinity, calcium, magnesium) but what about strontium, boron, potassium, iron, iodine, etc... Eventually these will all dwindle and they are also important to the health of corals.

 

[ScottB]

@Jdubyo has discussed depletion already. The flipside also warrants consideration: unwanted buildups of miscellaneous contaminants.

There are many many folks that run without WCs. Most/many of them:
a) take special care with source water quality (ATO water)
b) run a Triton or other ICP several times a year to see what is depleting or accreting in the system.
c) Follow a regimen (Red Sea, Triton, etc) to replace depleted building blocks.

 

[stanleo]

You can stop doing water changes as long as you are testing and dosing for all of your other elements. You have the big three down (alkalinity, calcium, magnesium) but what about strontium, boron, potassium, iron, iodine, etc... Eventually these will all dwindle and they are also important to the health of corals.

So the debate boils down to; is it worth it. Do I test for several more elements weekly and figure out the dosing requirements for those elements just to save a little money on salt and about an hour of time every two weeks? Thank you, I think I will just keep up with the water changes.

 

[Daniel@R2R]

Water changes are about importing trace elements and exporting nutrients. As long as you have a strategy/plan for this, you should be fine. Water changes are a tried and true way to accomplish this, but there are multiple other methods.