Water changes: Weekly to Monthly

[samuel2011]

Hi everyone,

I have been doing weekly water changes since about two years ago for my 5 and 20 gallon mixed reef tank.

For the past few months, I have switched instead to a monthly schedule thinking that I could make up for the less frequent water changes by adding nutrients such as trace elements and dosing ca, alk and mg more often since my goal with water changes is more for adding nutrients than diluting waste.

Hypothetically it made sense, but over the past few months the health of my corals seem to have suffered, particularly stony corals; most lps and sps have receded.

My conclusion was that water changes probably rebalance important elements to corals that are difficult to measure and for me at least it was difficult to identify and manually add those nutrients to make up for the lack of water changes.

But I wanted to know if any of you have tried something similar and whether it failed or not? And why do you think it happened in your case?


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[slief]

Coral (as well as fish) don’t like big or sudden changes in water chemistry or temp. A large water change can have a larger impact on the chemistry of the water beyond just things like Ca, Alk, Mg and pH and even those can impact the health of corals if the change is sudden and drastic enough. Even a sudden 1 point change of alk can impact the corals and the smaller the system, the greater the impact from larger water changes. I’ve always found more frequent smaller water changes result in consistently happier tank inhabitants and greater stability in the system when compared to less frequent larger water changes. In my case, since switching from larger weekly or bi-weekly water changes to smaller automated daily water changes, my tank has thrived in ways it never did before. This despite the fact that the monthly volume of water being changed now is less than it was when I was doing the larger weekly or bi-weekly changes.

 

[samuel2011]

Oh that's quite an interesting observation. Thanks for the input.

Coral (as well as fish) don't like big or sudden changes in water chemistry or temp. A large water change can have a larger impact on the chemistry of the water beyond just things like Ca, Alk, Mg and pH and even those can impact the health of corals if the change is sudden and drastic enough. Even a sudden 1 point change of alk can impact the corals and the smaller the system, the greater the impact from larger water changes. I've always found more frequent smaller water changes result in consistently happier tank inhabitants and greater stability in the system when compared to less frequent larger water changes. In my case, since switching from larger weekly or bi-weekly water changes to smaller automated daily water changes, my tank has thrived in ways it never did before. This despite the fact that the monthly volume of water being changed now is less than it was when I was doing the larger weekly or bi-weekly changes.

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[der_wille_zur_macht]

It's really hard to provide meaningful input without more info. What parameters are you measuring and how? What and how are you dosing? When you do a water change, what parameters from the change water are you matching to the tank? What are your targets for everything and how much fluctuation do you get, while dosing and after a water change?

Stability is important, not just having the right numbers. Balance against "waste" is important too, it's quite possible to have a problem because nitrate or phosphate are too low and/or not stable enough.

 

[samuel2011]

It's really hard to provide meaningful input without more info. What parameters are you measuring and how? What and how are you dosing? When you do a water change, what parameters from the change water are you matching to the tank? What are your targets for everything and how much fluctuation do you get, while dosing and after a water change?

Stability is important, not just having the right numbers. Balance against "waste" is important too, it's quite possible to have a problem because nitrate or phosphate are too low and/or not stable enough.

Hi, I was just asking if anyone did something similar and what were their observations in terms of coral health.

But fyi I was measuring only Cal, alk and mg. I'm only dosing those three and a trace element supplement from seachem.

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[samuel2011]

Hi, I was just asking if anyone did something similar and what were their observations in terms of coral health.

But fyi I was measuring only Cal, alk and mg. I'm only dosing those three and a trace element supplement from seachem.

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*in terms of coral health and etc.

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[RioReefr]

There are a lot of minerals in natural sea water (NSW). I don't remember the exact number, but it is something like 80+. There is more to the water chemistry than just the Mg, Ca, Alk that most measure. By doing regular, small water changes you are replenishing those trace minerals that may or may not be lost/used. Also, there is always going to be some "waste" (ie Nitrates) in your tank. You are striving to dilute this waste with pure water changes. As someone else mentioned, if you are doing large water changes then you are changing the water chemistry too much -- pH, Alk, etc.
IMO, the day I do a 10-15% weekly water change my fish just look "happier". Without a doubt, I am convinced the weekly water change would be far better than monthly. On another note, I have been recently dosing vitamins/amino acids and my corals never not looked better.
My tank is small (32G), but every Saturday morning I spend 1-hour doing my weekly maintenance -- water change, replace Carbon, clean powerheads, etc. Its really not much effort IMO to stick to a weekly maintenance schedule.

 

[d0ughb0y]

I'm going to venture a guess that your coral health declined after reducing water change frequency due to rising nitrates, which I did not see you mention you test for.

and yes, I have reduced the water change freq on my tank, but only after I can see that filtration is able to keep up with bio load.

 

[der_wille_zur_macht]

Hi, I was just asking if anyone did something similar and what were their observations in terms of coral health.

But my point is, me saying "I reduced/increased water change frequency and corals got better (or worse)" doesn't mean anything, unless my tank is exactly like yours in terms of parameters, livestock, feeding, lighting, stability, growth rates, stocking density, etc etc etc. There are simply way too many variables to address a question like this in a vacuum.

 

[2_zoa]

It's really hard to provide meaningful input without more info. What parameters are you measuring and how? What and how are you dosing? When you do a water change, what parameters from the change water are you matching to the tank? What are your targets for everything and how much fluctuation do you get, while dosing and after a water change?

Stability is important, not just having the right numbers. Balance against "waste" is important too, it's quite possible to have a problem because nitrate or phosphate are too low and/or not stable enough.

Hi, I was just asking if anyone did something similar and what were their observations in terms of coral health.

But fyi I was measuring only Cal, alk and mg. I'm only dosing those three and a trace element supplement from seachem.

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I believe what der_willie_zur_macht is getting at. Is that your not providing enough information for anyone to help you. Maybe you don’t want any help?

You made the decision to move to a monthly water change for a reason. It isn’t working out for you though. There is no reason you can’t do monthly water changes. Many people do them monthly. However, you can’t just do a water change blindly if you don’t know what the water change is going to do to the water parameters. You’ve stated you test your water for Cal, Mag, and Alk. What you don’t say is. What those numbers are and more importantly you don’t say that you’ve taken the time to have your water change water match the levels in the tank. What if your water change water has lower Alk then your tank has because of your dosing? Your going to change that parameter with that water change.

Also, what der_willie was saying is. What is the nitrate or phosphate levels at before the water change? Your going to affect those parameters with the water change. If you drive those numbers to zero, your corals will pay the price. It’s simple math. If you do a 50% water change you going to cut the nutrients in half. If your nitrate is at 5 and your phosphate is at .01 then a larger water change will do more harm that good.

Again, if you aren’t looking for help. You just wanted observation from others. Then I personally would have posted a Poll type thread and had others vote.