Why a weekly 50% WC is better than two weekly 25% WCs

[ScatMan]

I understand all that fully. But what I'm saying is, regardless of nitrates, the difference in changing you water weekly vs biweekly after one month is 3.76% (3.76% more water changed when it's done weekly). Whether it be a 10g tank or a 1000g tank, that percentage is still the same.

Is 3.76% of a tank's volume over a one month period enough to make a discernible difference in nitrate levels that's worth debating over? I'm almost certain the answer is no. Take for example a 300g tank, that's 11 gallons of water. How much of an effect on nitrates you think you're going to have if you change 11g of water?

i'm not the one arguing over whether or not it matters to me, i'm simply saying that 1 big change is better in the respect that it is less work (however negligible it may be) and that it reduces your average nitrates (however negligible it may be).

in op's example, it made a difference of 5ppm. whether that matters to you or not is a different debate entirely and frankly one i don't care to have.

 

[Dan F]

This argument is fairly interesting from a mathematical point of view, but as Jose has said, it makes very little difference in the "real world".

Where more frequent water changes become absolutely necessary is in heavily stocked tanks. Even if I did 100% weekly water changes I would still have unacceptable (60ppm+) levels of nitrate after a week.

 

[vfc]

More fuel for the debate. Looks like larger WCs, over longer period of time, reduces the average significantly.

 

[Allan01230]

Basically you can never do too many wc's. A 5% weekly is better than none at all. The famed Discus breeder Jack Waitley changes 100% daily on his breeders tanks.

 

[calioutlaw1a]

Dang Scatman you are on it. I don't have much to add to what you've said, it's as if you read my mind.

Like I mentioned in my post above, if it fits in your schedule and lifestyle, who cares, it's all the same. When looking the effective percentages of water changed over a period of time, the difference is so miniscule, it's silly to claim one method is "better" than the other.

I understand all that fully. But what I'm saying is, regardless of nitrates, the difference in changing you water weekly vs biweekly after one month is 3.76% (3.76% more water changed when it's done weekly). Whether it be a 10g tank or a 1000g tank, that percentage is still the same.

Is 3.76% of a tank's volume over a one month period enough to make a discernible difference in nitrate levels that's worth debating over? I'm almost certain the answer is no. Take for example a 300g tank, that's 11 gallons of water. How much of an effect on nitrates you think you're going to have if you change 11g of water?

Your point is well taken, and again I'm not trying to change people's lives with this data. However, a subset of hobbyists fit the scenarios I gave, and there aren't any significant changes necessary to switch from biweekly 25%wcs to 50%wcs. I don't see why someone would not want to reduce the time and energy spent doing water changes while improving their water quality (however minuscule it may be). It simply makes sense.
Again we are now starting to see how chronic nitrate levels impact the health of our fish, and we really don't know how big of a difference, for example, an average of 30ppm vs 35ppm as in my examples will effect our fish.

You got it backward. For the 50% weekly, your bladder get relieved once a week, and when it's filled back up, you have to wait the entire week until it get relieved again. For 25% twice a week, you bladder get relieved every 3.5 days. Is it really that difficult? I can make it's easier for you.. Do you think it's better if you drink two bottles of water when you wake up, and hold it the whole day, go to bed, and wake up the next day to relieve it then drink another two bottles of water and go thru the same routine? Or would you rather drink a bottle of water when you wake up, relieve it in the evening, drink another bottle of water, go to bed, wake up, relieve it in the morning, then drink a bottle of water and go thru that same routine?


You're right. The numbers don't lie, but you didn't see that the fish in 50% weekly wc situation exposed to nitrate level of 40ppm, before the water was changed to drop it, while it doesn't happen to 25% wc twice a week

In both scenarios the max is 40ppm. However, with a 50%wc the average nitrate is 30ppm while with biweekly 25% wcs the average is 35ppm.

 

[MonsterMinis]

In both scenarios the max is 40ppm. However, with a 50%wc the average nitrate is 30ppm while with biweekly 25% wcs the average is 35ppm.




THe point is some schmuck is going to take this "data" and start up with the "less is more" yodeling instead of " more is better" approach. You are justifying every slacker who doesn't do regular water changes in their minds atm... As Jose pointed out it's a very slim margin...

and as I've pointed out I've seen, and I'm sure i'm not the only owner who has seen what elevated nitrates do to a system. And how the fish react/respond. not to mention every other valid variable thats been tossed out there.

If I where to skip a 25% water change and just do a 25% once that week.. opposed to someone who skips their 50% once a week. What do the numbers show then? Other then we're human and that does happen. Nitrates would build up to a more dangerous level.

On a purely numbers level your right, On a realistic application to husbandry practices. You're wrong. It's been proven by breeders and exotic fish keepers for years that you can never do to many water changes. Telling people 1x a week of 50% is fine... is Crap on toast.

This is why I sometimes hate science/labs/ect.

btw 9/10 I'de wager the owners who do 2x a week or more water changes often do more then just a "weekly 50%" and often do more depending on the current state of the tank. It's not just the simple water change itself but the general maitenace that goes along with it, the over-all husbandry habits associated with it. which are a variable you won't find in a lab.

The info is interesting.. but shoudln't be made in a blanketed statement to hobbyists in general. because it doesn't apply to the hobby 100%.

 

[jlnguyen74]

This argument is fairly interesting from a mathematical point of view, but as Jose has said, it makes very little difference in the "real world".

Very true. While some just focus on number with a calculator, they forgot to take it into consideration of what they're doing when performing water change. Water change is not only about taking water out of the tank, and refill it with water. It's also about vaccuming waste, debris, left over food, which is the source of nitrate

 

[jlnguyen74]

In both scenarios the max is 40ppm. However, with a 50%wc the average nitrate is 30ppm while with biweekly 25% wcs the average is 35ppm.

yes it does, look at the math again. ppm will max out at 40 in both examples.

Assume both tanks start 20ppm, with 10ppm increase every 3.5 days. How long does it take for a fish in the tank with 25% wc twice a week expose to 40ppm? How long does it take for a fish with 50% wc weekly expose to 40ppm?

 

[vfc]

Assume both tanks start 20ppm, with 10ppm increase every 3.5 days. How long does it take for a fish in the tank with 25% wc twice a week expose to 40ppm? How long does it take for a fish with 50% wc weekly expose to 40ppm?

Look at the charts; both scenarios never hit 40ppms; they peak at 32-35ppms.

 

[vfc]

Here are two charts comparing the OP's 20ppms/week of bio-load @ 50% weekly WCs and doubling the bio-load to ~40ppms/week (heavier stocked tank). I would think that 40ppms/week bio-load is more typical for the average monster fish keeper.