Tropical Fish Keeping - Aquarium fish care and resources

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-   -   Why Water Changes?: The Long Answer (http://www.tropicalfishkeeping.com/beginner-freshwater-aquarium/why-water-changes-long-answer-38618/)

MOA 03-05-2010 12:29 AM

Why Water Changes?: The Long Answer
 
Hello,

I build stocking spreadsheets in my spare time and one accusation I often hear from the people who use my spreadsheets is that it is unfair to base how many fish a person can keep based on their cleaning frequency and the amount removed. I have heard this argument for many years and finally decided to answer it in some detail:

http://sites.google.com/site/moashowmanyfish/why-are-water-changes-necessary

The above link essentially states that 1) not all waste products can be handled by live plants or filters, and 2) that partial water changes do definitely limit the amount of waste that can be in a given aquarium. Hopefully this post will help answer any questions that new aquarists might have about water changes in general.

MOA

1077 03-05-2010 06:32 AM

[quote=MOA;338183]Hello,

I build stocking spreadsheets in my spare time and one accusation I often hear from the people who use my spreadsheets is that it is unfair to base how many fish a person can keep based on their cleaning frequency and the amount removed. I have heard this argument for many years and finally decided to answer it in some detail:

http://sites.google.com/site/moashowmanyfish/why-are-water-changes-necessary

The above link essentially states that 1) not all waste products can be handled by live plants or filters, and 2) that partial water changes do definitely limit the amount of waste that can be in a given aquarium. Hopefully this post will help answer any questions that new aquarists might have about water changes in general.

MOA


Would agree with much if not all of the info. Does your research take in to account the benefits of substrate cleaning (gravel vaccuming), or lack thereof in arriving at percentage of waste created or left after water changes? or were we to consider tanks without substrate as models?
I understand the dilution through water changes and the effects of reducing waste. But perhaps even more benefits can be realized with regards to amount of waste removed with water changes if a portion of the substrate is vaccumed as well ,or at least that is my thinking. Water changes alone can only reduce /dilute what's in the water .

Austin 03-05-2010 06:50 AM

tl;dr

jk. I read some of it. Seems complicated. @_@ I'll read it more in-depth later but looks nice and detailed. :D

redchigh 03-05-2010 07:22 AM

Quote:

Originally Posted by Austin (Post 338257)
tl;dr

jk. I read some of it. Seems complicated. @_@ I'll read it more in-depth later but looks nice and detailed. :D

I think it's a wonderful theory, but maybe you should wait until FISH urine and feces are analysed before you could it as authoritive fact.
Just an idea. Not saying it's wrong at all.


Oh, just saw the chart at the bottom. Is it from experiance?
How did you calculate mg/g of waste?

Do any of the urine components exist in a gas form in nature? If so, some could diffuse into the air.
Also, your chart at the least would only be accurate in a non-planted tank (yes, I'm one of THOSE people) because the mg/g of waste doesn't seperate which ones are usable by plants and which ones are not.
Can you assume that, if a PWC every 1-2 weeks is required for a non or lightly planted tank, then a pwc every 3-4 weeks would be more than adequate for a heavily planted tank?

Looks extremely logical, and certainly COULD be right. (probably is.) (I read everything except the equations)
Regardless, good job. We need more responsible fishkeepers like you trying to improve the hobby for everyone.

just realised that could be taken as sarcastic. I promise it wasn't.

Big Fish 03-05-2010 08:04 AM

MOA, dude

Great piece of work. I love spreadsheets and database programs (I used to do db work for a living). Truly, wonderful work.

I am printing it and keeping it by my tank.

That must have taken a few days or more to put together. Thanks for the effort.

MOA 03-05-2010 08:33 PM

1077,

My spreadsheets are all based on the premise of using gravel vacuuming in conjunction with water changes, but the RWI factor is not. As I mentioned in the post, the RWI factor is simply a comparison based on frequency and percentage. Consequently, things like like plants and the specific cleaning routine will make a difference. Unfortunately, those kinds of computations are somewhat lengthy and I did not want to give new aquarists a ten-mile chart to sift through. As such, the spreadsheets use the added benefit of gravel siphoning but the chart is an independent consideration.


Austin,

Lol, the longer I live, the more I am convinced that life wasn't meant to be simple. :)


redchigh,

Good point about the fish urine problem. The sad fact is that I have not found a good source that discusses fish waste in its consituent compounds. If you know of a source that deals exclusively with fish waste (in compounds, not elements), I would be more than happy to use it instead of the sources currently on the site. I only used terrestrial urine data because I could not find another. Excellent point.

Yes, some urine components can enter a gaseous state and are thus not much of an issue, but not all (by any means).

The chart is accurate regardless of type of tank as it is only the RWI factor. If you keep less fish than average, have live plants, or use a large filter (efficient filter), then your r value (ratio of remaining waste per gallon) would change (remember that the RWI factor does not use r). Consequently, all that the chart indicates is a same-tank-to-same-tank comparison. For example, the RWI factor of a tank cleaned at 20% every seven days is the same as that same tank cleaned at 40% every two weeks. How much waste that amounts to, however, cannot be determined as r is unknown. Thus, my guidelines of 15 to 45 are just general guidelines. It is possible to have a RWI factor of 600+ if your tank is very clean (but most people could not achieve that low of an r factor, but my experience is that high RWI factors go hand-in-hand with negligence.

My spreadsheets, on the other hand, do calculate the r value and will allow users with a lot of plants to keep more fish than aquarists without plants or allow them to clean less often (some scenarios may allow more than a year between cleanings if r is low enough).

BTW, the mg/gal. was just used for the example. My spreadsheets use a biomass index based on the IFU number of all the fish in the tank as modified by the feeding schedule (heavy feeding will increase the estimated bioload per fish). I find that most average-stocked aquarium systems have about 7-15 IFUs per gallon.


Big Fish,

Thanks, but I should mention that data changes every day in the aquarium world. Tomorrow someone could come up with something even better (and I would be happy about that).



MOA

MOA 03-06-2010 01:24 AM

Okay,

I edited the article to reflect the comments of people on this, and other, fish forums. Hopefully, you guys will find it a little cleaner and easier with regard to pinpointing my exact philosophy.

MOA :-)

iamntbatman 03-06-2010 03:31 AM

Terrestrial urine is quite different from fish urine. Because freshwater fish live in water that's much more dilute than their blood, they expel extra water that's almost completely free of dissolved materials. They also release ammonia directly into the water via their gills rather than producing urea. Freshwater fish urine is extremely dilute compared to that of terrestrial animals and is essentially just water.

MOA 03-06-2010 09:55 AM

Lol,

Yes, I know. I changed the article to reflect the aforementioned fact. :-D

MOA

small echinda 03-06-2010 10:49 AM

great data


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