Big water change VS. many small ones

Scotticus · Jul 4, 2012

I have been doing a little research into large water changes to reduce my nitrates. I had an anemone go awol into my power head about two weeks ago (the only one without a sponge on it of course), and my nitrates have been elevated ever since. I have read some articles that have shown large water changes to reduce nitrates can help without being detrimental to the tank. I was a little wary about trying it but I just can't seem to get them lowered. in the last three days I have lost two frogspawns, a blastumosa, a birdsnest, and I have a chalice on it's way out. So I think I'm going to take the plunge and do a large water change tonight. With losing all the corals I think the large WC is worth the shot. I also lost two fish within an hour after the anemone died but was able to save the two clowns that are now in a ten gallon hospital tank and doing very well. I want to get them back home so I think its time to try a rapid nitrate reduction water change 80% gone 80% new. Wish me luck I will repost when all is said and done with the results.

Pappy · Jul 4, 2012

Jair did 50% because of nitrates out of nowhere and everything is super happy! Nitrates dropped from 60-80 to 10. Did another 30% and haven't tested yet but I'm positive their good now!

Mike D "like the beastie boys" Sent from my iPhone using Tapatalk

Reefer831 · Jul 4, 2012

beaslbob said:
This water change question is very common.

So let me give a more unemotional math type anwser.

consider this

concentration before water change=concentration in replacement water+(concentration change between water changes)/fraction of water changes.

So if you change 1/10 of the water with 30ppm water and there is a 20 ppm increase between water changes you get:

concentration before water change=30ppm+(20ppm)/(1/10)=30ppm+200pm=230ppm.

If you're interested consider water changes that are %1/day or multiples like 10% ever 10 days, 20% every 20 days etc.

And the water as 0ppm nitrates and the tank is increasing nitrates a 1ppm/day.

What would be the nitrates centration before water changes?

answer 100ppm for all possibilities.

the amount after with water change would vary more as stated above.

So to me, much flames on other boards, and poo-hooed by experts what is important to me is to get the 1ppm increase down to unmeasureable levels. When you do that nitrates are just unmeasureable all the time regardless of wter changes.

And to buffer calcium/alk/mag so they are not dependant on water changes as well.

So I ran my tanks ran for years with no water changes.

my .02

I am seriously interested in what you mare talking about, but I dont completely understand you theory.... can you please post that in english? :wink:

Young Frankenstein · Jul 4, 2012

Large water change to fix, nitrates, ammonia, anything thats seems wrong. Small water changes to maintain following with additions of additives such as ca, mg, alk.

lpslover · Jul 5, 2012

beaslbob, with all due respect it sounds like you have two somewhat contrary arguments going here. If I understand correctly:

Argument A: Was discussed in Coral Magazine about a year or so ago on the mathematics of water changes. Primarily that if you assume waste accumulation to be constant (ie unchanging) doing a 10% water change every day for 10 days may still result in a 100% water change, but will leave the tank with far more waste remaining than doing a single 100% water change on the 10th day. About 50% more if my memory serves. Thus doing less frequent but substantial water changes is an excellent method for waste management (concerns over stability aside).

Argument B: Water changes are not an efficient way to manage waste. The emphasis of aquarium husbandry should be on reducing waste production and/or accumulation. I would assume by this you mean tactics such as not overstocking or over feeding, powerful water flow, efficient filtration, and biological export methods like refugia and carbon dosing.

Am I understanding your statements correctly? Care to clarify? Does one argument prove true in one case but not in others? How do you use either or both of these strategies?

ritter6788 · Jul 5, 2012

I change about 20% every 2-3 weeks. I dose Ca and Alk in between and my oversized skimmer helps to remove waste so it's not left rotting in the tank. Occasionally I run GFO and carbon when needed. I also try to match the chemistry of my tank water to the incoming new salt water parameters. That is one of the reasons I avoid salts with higher than normal parameters like Coralife (520 Ca) or Red Sea Coral (12-13dkh).

I think it's like everything else in this hobby. What works for one will be best for the other. I think a smaller tank with no skimmer would benefit from smaller, more frequent water changes than a larger tank with heavy filtration and dosing set ups.

beaslbob · Jul 5, 2012

Reefer831 said:
I am seriously interested in what you mare talking about, but I dont completely understand you theory.... can you please post that in english? :wink:

Don't get lost in the equations.

First the equation reflects where the tank would wind up. In order for that to happen the build up between changes must be removed by the water change. Change 10% the tank builds up to 10 times. 20% 5 times, 1/3 three times etc etc etc.

my .03

beaslbob · Jul 5, 2012

lpslover said:
beaslbob, with all due respect it sounds like you have two somewhat contrary arguments going here. If I understand correctly:

Argument A: Was discussed in Coral Magazine about a year or so ago on the mathematics of water changes. Primarily that if you assume waste accumulation to be constant (ie unchanging) doing a 10% water change every day for 10 days may still result in a 100% water change, but will leave the tank with far more waste remaining than doing a single 100% water change on the 10th day. About 50% more if my memory serves. Thus doing less frequent but substantial water changes is an excellent method for waste management (concerns over stability aside).

My analysis assumes a constant change not constant conditions.

Argument B: Water changes are not an efficient way to manage waste. The emphasis of aquarium husbandry should be on reducing waste production and/or accumulation. I would assume by this you mean tactics such as not overstocking or over feeding, powerful water flow, efficient filtration, and biological export methods like refugia and carbon dosing.

Am I understanding your statements correctly? Care to clarify? Does one argument prove true in one case but not in others? How do you use either or both of these strategies?

The equations should help one determine which is more effective. My position is simple that is it better to balance out a stabliize the system then to rely on water changes.

lpslover · Jul 5, 2012

I agree with you beaslbob that trying to attain balance that does not strictly require water changes to maintain is the goal, and that relying only on water changes for nutrient control is fighting a loosing battle, but I would not go so far as to say water changes are completely without merit. Just my .02.

beaslbob · Jul 6, 2012

lpslover said:
I agree with you beaslbob that trying to attain balance that does not strictly require water changes to maintain is the goal, and that relying only on water changes for nutrient control is fighting a loosing battle, but I would not go so far as to say water changes are completely without merit. Just my .02.

And neither would I.

Under ememgency conditions then sometimes a water changes is mandatory. Or moving livestock to another tank until the tank can heal.

but for routine operations IMHO it is better to balance out the tank. And again for routine operations water changes only mask underlying problems that are best corrected through other means.

my .02

To your .02

to my original .02 :xd:

Mike&Terry · Jul 6, 2012

We have had a couple of occasions where we've done a very large water change w/out any issues. We use Tropic Marine Pro Reef, so do not have to worry about alk swings and such.

Our typical water change schedule is 10-15% weekly.

robf · Jul 23, 2012

I just bought a RENEW automatic water changing system to do small continuous changes to my 300 gallon system. Haven't installed it yet but the plan is to do small changes over a long period of time. I'll let you know how it works. The idea is simple and with a few float switches and a good bit of logic you too can replicate the RENEW system using aquarium controllers IMO.

Big E · Jul 23, 2012

Water changes aren't just about reducing nitrates & phophates from the perspective of strictly swapping out water. Most people are sucking up detritus & other nasties which produce nitrate & phosphate. I blow off my rocks with a baster before I do my water changes & then catch & suck up all the crap that settles with my water change. Eventually the rock gets clean & won't harbour algae.

There are also numerous elements that aren't measured by test kits that get used up. There is no other way to replenish these without doing a water change. Doing smaller whater changes is the only way to keep the tank" balanced"...........not doing any changes is the worst way to keep that balance........think outside of the few things we test & it's obvious.

I've been doing 10% weekly for over 20 years & have never had a tank crash or any of the other issues people have with corals not doing well.............been keeping acros for over 12 years.

Randy Holmes F. has a good article about water changes...........good read.
Water Changes in Reef Aquaria by Randy Holmes-Farley - Reefkeeping.com

kuyatwo · Jul 23, 2012

Big E said:
Water changes aren't just about reducing nitrates & phophates from the perspective of strictly swapping out water. Most people are sucking up detritus & other nasties which produce nitrate & phosphate. I blow off my rocks with a baster before I do my water changes & then catch & suck up all the crap that settles with my water change. Eventually the rock gets clean & won't harbour algae.

There are also numerous elements that aren't measured by test kits that get used up. There is no other way to replenish these without doing a water change. Doing smaller whater changes is the only way to keep the tank" balanced"...........not doing any changes is the worst way to keep that balance........think outside of the few things we test & it's obvious.

I've been doing 10% weekly for over 20 years & have never had a tank crash or any of the other issues people have with corals not doing well.............been keeping acros for over 12 years.

Randy Holmes F. has a good article about water changes...........good read.
Water Changes in Reef Aquaria by Randy Holmes-Farley - Reefkeeping.com