Water Changes - Is Even More Better?

Roan Art

Roan Art

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Like most people, I'm on the weekly regime of 50% once a week, however my betta blew a couple of rays and I started changing out his water every 3rd day for a couple of weeks. Since my 36g is close by, I did that one as well.

I could not believe the difference 2 or 3 50% water changes a week made in my fishes' colors and behaviour. The rainbows were MUCH brighter, my neons and glo-lites glowed and their general well-being seemed to increase two-fold.

So my question(s) is/are: should we not be doing more frequent water changes? Is that really the MINIMUM we should do to prevent disease? *Why* do we only recommend 1 a week?

Roan
 
Roan Art said:
So my question(s) is/are: should we not be doing more frequent water changes? Is that really the MINIMUM we should do to prevent disease? *Why* do we only recommend 1 a week?

Roan
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thats a really good question... i think its a good bench mark for someone new to the hobby. the freqency is enough in most cases, and too much manipulation can be a bad thing too... for instance, if you are not using enough dechlor per change or not replacing at proper temps....

but in reality, as people get to know their tanks, i think it ebbs and flows. i'd be an outright liar if i said i changed water every week, but then again, sometimes i change four times in three days if something seems suspicious or i want to 'polish'. the noise is enough after ten days or so (evaporation) to prompt action most times.

i think the emphasis should be on topping off a tank to get the proper volume change for the guidelines to apply...

i've always thought that a 50% water change is reserved for emergencies, but thats just me. ~30% is where my 'enough' switch hits. depends on the waters that day, really.

:cool:
 
If this is not a planted tank, I would only do once a week as to not reset the cycled tank. I would think if you kept doing changes say every third day, you will eventually reset the bio capacity. But if you were changing the water every third day, the bio capicity would mean very little. However, if there were any problems with the tank or one is taking out meds, I would do more than once a week without any hesitation.

Also, Doing a water change every 3 days can be quite annoying. Really, the water change is to help minimize the creep of ammonia, nitrite and nitrate imo for a non planted tank. My fish do very well in my non planted tank and have great color (bright yellow or deep black) and eat well. I do a 40% change once a week (most of the time).

For a planted tank, I do one 50% once a week and two smaller changes - say 5-10% or so to help things out. Mainy the extra changes are for the plants to add more natural traces and to keep things moving smoothly.

My $0.02

Aries
 
More water changes is definitely "ideal", but most folks don't have the time or patience, and it's certainly not necessary to keep healthy fish.

Consider that in nature there's an almost constant renewal of water - in most places. However, the *minimum* water changed for healthy fish and long term care is best judged (in an unplanted tank) by the NO3 level. Empirically a level of 20 - 40 ppm is usually advised. Personally, I prefer to err to the low side since this is really an unquantified method and test kits are really only 50/50 anyway. Is 20 ppm on the test kit significantly different than 40 ppm, maybe, but maybe not. Whenever this kind of ambiguity exists, it's always best to err on the side of caution.

For what it's worth, 2 30% changes amount to the same net water change as a single 50% change, unless you can a 1% difference in tank volume.
 
Aries said:
If this is not a planted tank, I would only do once a week as to not reset the cycled tank. I would think if you kept doing changes say every third day, you will eventually reset the bio capacity. But if you were changing the water every third day, the bio capicity would mean very little.
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Aries, the size of the bio-filter is based on (assuming that there are no space limitations) the available ammonia supply. Changing water doesn't affect this in a significant way. Now if you were changing 100% of the water daily (or better yet, a flow through device), you may get into the situation where no ammonia would reach the bacteria and they would die off. However, ever changes of 30-50% daily won't significantly impact the size of the biofilter in a cycled tank.

Consider that proper filtration will run through 3-5 tank volumes per hour. In a 24 hour day that means that the filter bacteria "see" the tank at least 72 times (ideally 120 times) and feed of ammonia production. Compare that with a 50% daily water change, your bucket "sees" half the tank in a day, at this rate you will not outcompete the bacteria for available ammonia and nitrite. All you're able to do is remove the excess, that which nothing consumes on a time scale faster than your removal rate, notably various organic compounds and NO3 (in an unplanted tank).

In a cycled tank, ammonia and nitrite should be 0 ppm, always. If you need to do water changes to keep these from increasing, your tank isn't cycled.
 
Aries said:
If this is not a planted tank, I would only do once a week as to not reset the cycled tank. I would think if you kept doing changes say every third day, you will eventually reset the bio capacity. But if you were changing the water every third day, the bio capicity would mean very little. . . .
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Aries,

I'm not quite sure I follow what you are saying here. Isn't the bioload determined by the number of colonized bacteria? I understood that the bacteria do not colonize the water column, but surfaces of the tank such as the filter, gravel, rocks, etc.,.

Could you clarify what you mean, please?

Roan
 
I've been keeping a 25% weekly water change in my 235 gallon. This tank has a relative low bioload, so this much is quite enough to keep it sparkling clean.

On the other side, I do a 50% weekly in the 20 galloner. This one has 1 goldfish and a koi, and that "large" change keeps the nitrates steadily at 30-40 ppm. I hope I can get a bigger tank soon.
 
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