Signs I might need to do a water change?

Ssteve

New member
So quick specs on my tank is its a 120g sps dominated reef, I run a CalRx, small refugium, a 40w uv(bulb hasn't been changed in over a year). Medium bioload(three medium tangs and 8 other small fish) and I skim pretty heavy with a vertex 180. No other filtration. No filter socks, no floss, no carbon, no gfo etc. The tank is about a year and a half old now I think and its been doing great for the last 8-9 months.

As for water changes, I did religious large water changes for the first year. Approximately 20-30 gallons every two weeks, because if I didn't do them my sps would suffer and I would start getting algae issues. At around the 8-9 month mark when everything was stable and no equipment changes were being made, I started doing smaller WC and the times in between them stretched out a bit with no negative affects.

About 4 moths ago I decided to let the tank go for a while and see how it responded without a water change. Everything did great, amazing growth, great PE, my alk/cal consumption was at an all time high etc. Then about 2 month in I decided to do a water change. Not for any reason, just cause I figured it would help with the trace elements and what not. Did a 20g WC just as I have done many times before, same salt, same parameters etc.... The tank didn't like it though. It took about 3-4 days to see normal PE and alk consumption and I had two small acros bleach out.

So here I am, two months later. Tank is doing great, I keep needing to up my Co2 cause everything is growing like crazy, colors are great, PE great etc. Yet I am still wondering, should I do a water change or should I just leave it alone? And if I leave it alone, what should I be looking for before I do decide to do a water change?

before anyone asks..... I don't test nitrates, nitrites, phosphates etc. I did when my tank cycled and then after that I was doing it every once in a while but found myself just chasing numbers so I stopped. I primarily just test Alk. Normally about 3-4 times a week but sometimes calicum and magnesium as well.

Additionally I can not keep many softies alive. Most zoas melt, my colony of duncans grow but rarely ever extend and the amount of flow I have would rip up most fleshy stuff so I don't even try.
 
You answered your own question. You don't test. The only true way to know what parameter(s) possibly changed is to test before and after the WC. Now I will say that a 20g WC in a 120g system represents less than 20% (even less if you didn't include sump water volume).

So, it's unlikely that a change of that minor volume changed anything dramatically which is why livestock rebounded within a few days.

I highly suggest if you plan to do another WC, test before and 24hrs after.
 
+1^ Testing is a sure fire way to know (nitrates and phosphates will go up or be high, calcium ALK will be low to name a few). Also when nuisance algae and other unwanted things (can't keep softies or Zoas) start happening, its usually a sign a water change is in order
 
By the time you see any signs its too late.

I would start changing water again, because once it crashes the water fouls quickly

Stay ahead of the train, don't wait to see the lights or it will run you over.
 
More and more tanks are going no water change. Results so far seem pretty good for many. Seems you followed the steps that FarmerTy advocated in his thread. Slowly backing off the changes as the tank matures and settles in.
 
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