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

XanAvaloni,

Grammar error fixed--the catch was appreciated.


THE V,

Excellent point about the misnomer regarding urine conventions. My overall point in that section was not that urine had a definite content, but that the content was complex and that it is unlikely that any system can account for every single component (even the best tanks are subject to ion accumulation). That is the only point that I was trying to make. Perhaps that is one part that I will completely rewrite--I agree that it is unfair to use a terrestrial source in place of the piscine. Good catch.

Also, the rest of my article does not rest "upon the idea the assumption that the fish waste is not used by other organisms." You will note that the more complex equation uses the variable r, which stands for the "ratio of daily IFUs per gallon." In more detail, the effectual daily IFUs per gallon is the fish waste as modified by bacteria and plants (a computation I use in the spreadsheets, but not in my examples as they are too long). Thus, a low r factor would decrease the overall waste of the system--allowing for a longer cleaning period. Of course, the chart at the bottom does not include r, which I state in the article, and is thus "a relative cleanliness index to a particular aquarium system." This means that the chart only compares one tank to itself: at tank cleaned every 8 days at 30% will be just as dirty as one cleaned every 12 days at 45%, etc.

As to the shift in my argument that you suggest, I cannot concur: it is impossible to predict exactly how "balanced" a particular arrangement of plants/microbes and fish will be in that the specific requirements of most species are not precisely known. Consequently, one odd substance my be produced in a greater quantity than is truly needed. This imbalance can sometimes only be found with the aid of a fully complemented laboratory--which most home aquarists do not have. Therefore, my argument is that since it is impossible to be sure of a completely balanced system, it is safer to simple do water changes from time to time instead of hoping that the system is perfectly balanced out.

No less, I still agree that I need to rework the section talking about fish waste and that I need to be more obvious about the importance of the r variable. Very good points.


Scuppers,

"For me? well water tests twice a month and water changes twice a year....BASED ON OBSERVING MY FISH AND THEIR HABITAT"

You are assuming that your observations are accurate and that the test kits show all of the vital statistics--they don't and you aren't a fish. In other words, it is very arrogant of us aquarists to assume that we understand our fish so well so as to think that we know what is comfortable for them (don't forget that is once argued that African Americans were comfortable being slaves). As to the test kits, I used to work in the College of Southern Idaho Laboratory and one of our tasks was aquacultural analysis: test kits do not measure Arsenic or other heavy metals like mercury, and fail to account for trace accumulation of any kind. Consequently, test kits only warn the aquarist of a major problem--and that in retrospect. Fairly frequent water changes, on the other hand, work in the role of prevention. I also used to sell fish and can attest to the value of preventive measures--I made a lot of money off of people who only did a water change when the test kit said they should, lol.

No less, I am not being fair as you did mention a heavily planted tank, which has preventive attributes as well. If you do have a a very lightly stocked tank, then twice a year cleanings may be sufficient. Regardless of sufficiency, I am not interested in getting away with anything (including seeing how long a tank can go without cleaning). I have never seen a tank less frequently cleaned do better than one more frequently cleaned (all other conditions equal), never. If the system is as efficient as you suggest, then a water change executed more frequently should not be a problem. Why try to avoid something that is inherently beneficial?


Aphotic Phoenix,

"You're dealing with an issue of osmotic pressure regulation due to TDS"

Um--NO. I was not thinking of osmotic forces at all, was thinking of the trauma of having more than 30% of your home removed after a long period of environmental stability. People get so caught up in considering the science of fishkeeping that they become insensitive to the fish's perspective. Place yourself in the position of the fish--would a major water change scare the **** out of you? Yes, yes it would. My point is that fish that are not scared tend to have healthier immune systems, which equates to a longer life span. My point in suggesting caution for water changes above 30% is that fish have to be acclimated to a routine to be comfortable with it.

In trying to be fair, you are right that I did not give much explanation and that I did not mention substrate cleaning at all. Good points and well thought out.



MOA

Hello Again,

I agree with you. My basic point is that water changes = good, not thinking = bad. As to the chart, I clarified some of the surrounding language, but people are always going to intepret things how they want to. Also, larger, less frequent is the same thing as smaller, more frequent if one is talking about remaining waste (which is what the chart is labeled as pertaining to).

Also, as a general note to everyone (who have been very kind in pointing out various errors), I have changed the entire article so that it draws a distinction between the science of fishkeeping and my personal philosophy of fishkeeping. I realize that many of you will not necessarily agree with my philosophy (it takes all kinds), but I felt it necessary to make it clear that my work is very much based on a particular set of premises. I appreciate the comments you guys (and possibly gals) have offered and look forward to hearing what you guys think about the revision. I appreciate that you guys are not afraid to disagree .

MOA