For starters, you need to read the entire post under the heading: No Water Change In Six Months that I wrote. Actually it's 16 months since the last water change.

But what you people fail to realize, the tank automatically evaporates its waters, so I place in chemical-free water in the tank each week, approximately 3-4 gallons of fresh new water. If you add that up, it amounts to about 36 to 48 gallons a year. In the 55 gallon tank, the tank recycles itself naturally once (at least) fully each year. Because the tank is open at the top (or no fluorescent instead only natural sunlight) the water evaporates, and I find during the winter, when the heater is raised, the water evaporates even more so.

So the tank does recycle itself naturally.

As for current, I do have two bubble disks in the tank which provide plenty current for the stream/river fish in the tank; second, the bubbles that explode at the top or on the water surface provide plenty oxygen.

Lately, now that I have had the tank for nearly 5 years now, and I observe the inhabitants to the point that I know when there is a problem - and by the way, I have not had a fish death in 17 weeks; the last fish death was caused by the redtail shark irritating one of the zebra danios - so I have cut back on the liquid tests for ammonia, nitrite and nitrate to every 6 weeks to 2 months. The last time I tested - I keep a daily log on the tank - January 27, 2013, temperature: 78-82, ammonia: 0; nitrite: 0; and nitrate: 20. The testings are well within normal.

So your assumption without actual experience in this type of natural ecosystem is ill-founded. To call it "nonsense" is absurd without actual experience in this type of ecosystem. In fact, anyone who believes what I have been doing is stupid or morally wrong, those ideas or judgments are ill-founded for they are not based on actual experience.

As I asked once before on this web site and another one - I have yet to have anyone explain otherwise - if we use liquid test kits to test for ammonia, nitrite and nitrate, and our tests show the tank is registering normally, then the liquid tests were accurate or just fine and dandy. On the other hand, when I use the same liquid tests, I obtain the same normal results, but because I have an all natural ecosystem, something is wrong with the tank.....I have yet to have someone make heads or tails out of this paradox. In my humble opinion, it is simply a matter of ego....I AM RIGHT!

I agree with no water changes. I have a beautiful 75gal freshwater tank and have never done a water change since I set the tank up a year ago. I do add around 7 to 9 gal of water weekly due to the water evaporation. My fish are healthy and active.

I do add good bacteria to the tank every 8 wks and add chlorine/ammonia killer when adding the water replacement wkly is all. I have always believed if the tank is well balanced with bacteria, fish, bottom feeders etc the tank can pretty much maintain itself.

Did the same time years ago with a 150 and 75 gal.