Giant Water Changes - Good or Bad?

that Reef Guy · Apr 22, 2014

I have heard that Giant Water Changes are great from some people while other people tell me it is a terrible idea.

I always thought that they were a good thing.

The way I see it is you add a ton of Calcium, Magnesium, and Trace Elements.

And also take out a ton of the waste keeping your Nitrates at O which is great for Coral Growth and keeps Algae Down.

What do you guys think?

mfief · Apr 22, 2014

I have recently started doing 15 gallon water changes on my 55 gal (instead of 10). My corals weren't acting right and I was getting a lot of algae growth. Everything started acting up when I started vacuuming the sand bed. I am slowly removing some of the sand because it is just to deep for my liking. I have done the 15 gallon change 2 times now. I am getting into the sand bed on the first five gallons the just taking water for the last 10. The algae has stopped spreading (knock on wood) and the corals seem much happier, especially the acans, zoas and palys

Waters · Apr 22, 2014

What exactly are you defining as a large water change? If you are talking about 50% of the water, than I wouldn't think that would be a good idea (but I could be wrong). Any quick change to the water chemistry would not be good for any sensitive fish or invert. I was always told that frequent small water changes are better than infrequent large ones. I currently do weekly 10 gallon changes on my 60 (with a 20 gallon sump).

ReefMadScientist · Apr 22, 2014

Ive never seen anything bad happen. Make sure the water temp is exact.

mfinn · Apr 22, 2014

If the purpose is to add elements back into the water and they are low enough that you have to add a ton to make up the difference, or take a ton of nitrate out of the water, then your probably doing more harm than good by letting the tank get in that condition in the first place.
Regular water changes are best.

Jeff.:P:. · Apr 22, 2014

I do 50-100% wc on my 6g nano every week.
I have daily visible growth on my Digis and acros. So far so good!

jcdeng · Apr 22, 2014

It is good if you can match up the new water to your tank water's parameter 100%. Really bad if not, example, you do a 90% water change, your DT water is at 9.5 dKh alk. Your newly mixed water (which most salts will give you 7dkh cuz thats close to NSW). You then proceed with the WC, 9.5 -> 7 dkh in 1/2 hour. Then you just caused a big alk swing.

lisa28 · Apr 22, 2014

Jeff.:P:. said:
I do 50-100% wc on my 6g nano every week.
I have daily visible growth on my Digis and acros. So far so good!

With such a small amount of water wouldn't that be necessary? do you have any type of filtration?

ValorG · Apr 22, 2014

If you were matching most of the main parameters like temp, alk, calc levels. Then doing 50-60% water changes Shouldn't be a problem. But I usually just match temp and alk and do no more than 35% at a time.

Reefing Madness · Apr 22, 2014

ReefMadScientist said:
Ive never seen anything bad happen. Make sure the water temp is exact.

Making sure Temp, PH, CAL, MAG, SG and everything else is the same, and doing large water changes shouldn't affect anything.

zesty · Apr 22, 2014

ValorG said:
If you were matching most of the main parameters like temp, alk, calc levels. Then doing 50-60% water changes Shouldn't be a problem. But I usually just match temp and alk and do no more than 35% at a time.

This.

mfinn · Apr 22, 2014

Reefing Madness said:
Making sure Temp, PH, CAL, MAG, SG and everything else is the same, and doing large water changes shouldn't affect anything.

but since he already said that he is doing a giant water change to make up those elements, why would you add new water with depleted ca., alk, and mg?

that Reef Guy · Apr 22, 2014

Waters said:
What exactly are you defining as a large water change? If you are talking about 50% of the water, than I wouldn't think that would be a good idea (but I could be wrong). Any quick change to the water chemistry would not be good for any sensitive fish or invert. I was always told that frequent small water changes are better than infrequent large ones. I currently do weekly 10 gallon changes on my 60 (with a 20 gallon sump).

55 Gallon - I change 20 Gallons every week but the it seems more like 60 to 70 Percent is changed over 36% because Aquariums are always less Gallons that they claim and the Rock and Sand Displace Water too.
29 Gallon - 12 Gallons changed every week
10 Gallon - 4 Gallons every week
20 Frag - 8 Gallons every week

But all these Tanks seem to go down 60-70 Percent based on what I said above.

that Reef Guy · Apr 22, 2014

ReefMadScientist said:
Ive never seen anything bad happen. Make sure the water temp is exact.

I heat all the New Water Before I put it in so the Temperature is constant.

ReefMadScientist · Apr 22, 2014

Reefing Madness said:
Making sure Temp, PH, CAL, MAG, SG and everything else is the same, and doing large water changes shouldn't affect anything.

This...much elaborate than my answer but my thoughts exactly

Kworker · Apr 22, 2014

It really just boils down to if you can match ph, temp, salinity, etc.

If you can.. it would be efficient, but if you mess up.. it can kill.

Waters · Apr 22, 2014

KCbutnotsosunshine said:
It really just boils down to if you can match ph, temp, salinity, etc.

If you can.. it would be efficient, but if you mess up.. it can kill.

Exactly....which is why it is safer to do smaller water changes more often. If parameters are off.....it won't matter as much. To me it isn't worth the risk of doing huge water changes and have to worry about matching the water chemistry. All I need to check is salinity and temp.

vlangel · Apr 22, 2014

I serviced tanks for a LFS and I tried never to do more than 25% unless they were experiencing something catastrophic. From my experience smaller ( 5-10%), more frequent, (once or twice a week) WCs are the best.