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Discussion Starter · #1 ·
what is the purpose of changing the water? Is it a preventative measure to keep nitrates, nitrites, ammonia, hardness & the PH from getting to high. If the carbon, sponge, & bacteria in the biomedia keep the level of harmful chemicals at proper levels is it still neccessary to do water changes? Are there other things I am not considering that can harm the fish?
 

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While the biofilter takes care of ammonia and nitrite, it produces nitrate. The only way to effectively remove nitrates is to do a water change. Though nitrates are not very harmful to fish, they can be if they are allowed to build up. Changing the water also replaces the trace minerals that that the fish need. Also fish like new water. IMO fresh water is like fresh air. You know how the air is so nice out side........ fish like new water.
 

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Mikaila31 really said it very well, and I'm only going to emphasize it a bit because I'm concerned that you may be contemplating not doing partial water changes and that spells disaster in time.

Fish take in water through their cells (called osmosis) and expel it as urine after they have used it to do biological processes much the same as we do. In time, they would literally be swimming in a tank of urine. Not healthy for fish any more than for us.

As Mikaila31 said, fish need minerals and that has to come from water changes because they use up the minerals in the existing water fairly quickly. If it is a planted aquarium, the same happens with plants. The nitrates produced as a result of the nitrobacter bacteria do build up if not removed; mosat aquarist aim for nitrates around 20ppm or lower; at over 40ppm they are toxic to many fish. Plants utilize some of it through the action of the bacteria in the substrate, but if there are anaerobic bacteria in the substrate (as there usually are in varying numbers) they produce nitrogen gas and hydrogen sulphide. More toxins that need to be got rid of.

There is a small school of aquarists (I suppose there still are, I haven't come across any on this forum) that advocate it is unnecessary to do water changes in a thickly planted tank with few fish. I am skeptical of their claims, and would not want to risk it. Besides, like most of us I like to have lots of fish in my tanks, and without water changes I certainly wouldn't have them healthy for very long.

It is no surprise that fish will often spawn immediately after a significant water change. I know there are a number of reasons why this occurs, but the point is that without the water change they would not be motivated to spawn to the same degree. It's natural, and as Mikaila31 said, they like it.
 

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Overall I agree with the above, however I have yet to come across a fish other than discus that have issues with 40ppm of nitrate. There's been reports of some fish being fine at 100ppm, personally I would worry at this level. I run 40ppm of nitrates out of the tap and I dose nitrates on top of that. Ideally you want low nitrates, but I don't test for nitrates.....

"No water changes in a thickly planted tank that is lightly stocked". I do advocate this method, its called the El Natural method. Also a filter is optional. Though I don't run any tanks using this method(I stock heavily) it is a viable method. I'm not entirely sure how water nutrients get replenished using this method. Aquaticplantcentral.com has a whole forum section dedicated to El Natural style of fish keeping, I'm sure that question could be answered there. I'm an hour from the twin cities and in the summer people have successfully bred fish outside in large cattle troughs(100-300Gal) no heater or filter, some do water changes others rely on the rain. I'm hoping to give this method a try this summer.
 

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The theory of heavily planted aquariums not needing water changes is almost 100% correct. As far as the nitrogen cycle goes, yes you can have an aquarium without ever needing to do a water change. Outdoor ponds do it this way all the time. The difference though is that outdoor ponds rely on rainwater to replenish minerals, where you wont have this in an aquarium setting. However you wouldn't have to do weekly water changes because the fish don't use up minerals THAT fast. I would say to be successful in one of these "Natural" tanks, you would still need a water change every few months.
 

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nothing better than a breath of fresh air when closed up in a stuffy room.
my corydora catfish often spawn after a water change.
and all the other fish love them for it.yum yum.
 

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Overall I agree with the above, however I have yet to come across a fish other than discus that have issues with 40ppm of nitrate. There's been reports of some fish being fine at 100ppm, personally I would worry at this level. .
Besides Discus, Threadfin Rainbows,Celestial Pearl danios,Sparkling Gourami, Otocinclus,and German blue and Gold rams are a few other fish who do best with nitrates kept at levels below 40 ppm. Always best in my view,, to aim for 20 ppm.
 

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Discussion Starter · #8 ·
So the reason for water changes is to remove the built up nitrates & to replenish the minerals used by the fish. According to my testing kit hardness is the measure of calcium & magnesium & they are need by the fish to maintain correct balance between its internal body fluid & the external environment. So if the hardness is at appropriate levels is it still necessary to replenish the minerals or are there other minerals that the fish need.

Also I am not trying to argue against water changes. I am just trying to understand the reason for it is needed & to be able to determine when it is necessary to do so.
 

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I believe you pretty much understand it. Nearly all recommend weekly 20 to 25 percent water changes for long term health of fish in moderately stocked aquariums.
 

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Discussion Starter · #10 ·
I would like to determine how often changes are required for my tank. From this discussion it seem that nitrate levels & hardness should be used to determine when a water change is needed. At what values should I change the water. I have been recording the measurements for the last 80 days & graphed them & attached it to this post. the horizontal axis is the number of days since january 1st.
 

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As stated,, Water changes of 20 to 25 percent each week are generally agreed on for healthy fish to remain healthy. Many variables come into play in regards to how often a tanks water needs changed other than the two mentioned. Number of fish,species of fish,feeding schedule,tank size,filtration, maint routine or lack thereof,Temp of water (higher temps = higher metabolisim) Ph, (ammonia =more toxic at Ph 7.0 or above) . Types of foods offered (some foul the water quickly) You must take everything into consideration. A tank full of tetras could go longer between water changes than a tank containing Oscar or pleco.;-)
 

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Besides Discus, Threadfin Rainbows,Celestial Pearl danios,Sparkling Gourami, Otocinclus,and German blue and Gold rams are a few other fish who do best with nitrates kept at levels below 40 ppm. Always best in my view,, to aim for 20 ppm.
Very odd, Sparkling gouramis and ottos I've kept before. GBR and Threadfins I have right now. Sparklers I've spawned before in 40ppm of nitrate. I dose EI, so truthfuly my tests read 80ppm of nitrate, however as far as I am aware the nitrates I add via ferts are harmless.
 

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I think 1077 has summed it up best in the last post; regular partial water changes keep healthy fish healthy, and that's what it's all about.

The reaction/behaviour of fish when the water is regularly changed clearly demonstrates that there is probably a lot more benefit than anyone can measure in nitrate levels or hardness or whatever. A closed system can alter in ways we may not recognize however often we test for this or that. To gammahermit, I would never suggest only changing water due to certain test results, that in my view is meaningless, because there are all these other factors in the equation.

An aquarium is a closed system (aside from the exchange of oxygen/carbon dioxide at the surface) that does not exist in nature. Water changes are important in maintaining a healthy aquarium as it is the closest we can come to creating a natural environment for the inhabitants.
 

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Am pleased that your efforts have apparently been rewarded. My own observations of the afore mentioned fishes revealed nothing odd at all. The fishes did better with nitrAtes below 30 with 20ppm being ideal.Elevated NitrAte levels some believe,, Are not that detrimental to long term health,spawning success,and hatch rate. My own observations indicate otherwise. Always good to have measured opinions on nearly all topics.
In my view,, Elevated NitrAtes,elevated ammonia,and or nitrites all affect the ability of fishes blood to absorb and hold oxygen thereby increasing the respiration and stress levels which in turn,, affects the fishes health.;-)
 

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Discussion Starter · #15 ·
I would agree that periodic water changes are necessary for the fish to flourish but what I was hoping to get out of this thread was 1st understand why they are necessary & 2nd to figure out how often it is necessary rather than to just say every week or every month.

I would have to disagree with Byron that nitrate & hardness measurements are meaningless. But instead say they are insufficient to determine when a water change is necessary. And that with enough information it can be determined what the maximum time between water changes is.
 

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Indeed it is the combined information that dictates the frequency, or should ,, but there is no one formula.
 

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I would agree that periodic water changes are necessary for the fish to flourish but what I was hoping to get out of this thread was 1st understand why they are necessary & 2nd to figure out how often it is necessary rather than to just say every week or every month.

I would have to disagree with Byron that nitrate & hardness measurements are meaningless. But instead say they are insufficient to determine when a water change is necessary. And that with enough information it can be determined what the maximum time between water changes is.
Sorry, my fault for not making it clearer (that's the trouble with emails, we can't see what we're each thinking when we write words!). Tests for nitrates and hardness and pH and... are obviously important. But the time at which you do a water change should not be determined by test results. That's like saying you will only do a water change when something is wrong (the nitrates are suddenly higher, whatever). That is not good aquarium management. As I think several of us have indicated, regular water changes have an obvious effect on the health of the fish, and that is the bottom line. And everything I've read indicates changing less water more often is much better than changing more water less often. There is a real biological issue here.

The aim is to maintain consistent water quality permanently. This is not as impossible as some may think. There are fluctuations that occur naturally, in nature and in our aquarium. Fish have evolved to adapt to these minor fluctuations. This involves temperature and pH (there are diurnal fluctuations both in nature and in an aquarium), hardness, and dissolved organics in the water. Fish are very closely tied to their environment. As an example, fish take in water through their cells by osmosis. The fish must adjust its internal pH to equal that of the water passing into its cells. In an excellent article on "Fish Growth vs. Tank Size" in the December 2006 issue of TFH, Laura Muha notes that "Both salinity and pH affects a fish's growth rate because they affect how hard a fish's body must work to maintain its physiological equilibrium--that is, the complex chain of internal chemical reactions that keep the pH of its blood steady, its tissues fed, and its immune system functioning. When pH and/or salinity stray outside the ideal range for any given species, the fishes' bodies must work harder and use more energy to maintain this equilibrium." We all know how stress affects humans, and it is now known that this occurs with fish as well. Having fluctuating water conditions means the fish is constantly having to adjust its metabolism, and this stresses the fish and can lead to poor health, disease, and even death if not corrected. The point of regular water changes regardless of what the water conditions may be is that it is establishing an equilibrium in the tank and therefore in the fish, resulting in healthier and happier fsh. Changing 25-40% of the water every week is maintaining such a balance. This answers your questions as to why and how often.
 
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