Why are water changes necesary ?

[greenmaji]

dissolved protein, hormones, heavy medals such as copper, zinc, lead... the evidence isnt nessisary unless you can implement a filtration system that can remove these compounds then water changes are nessisary. its just common sense..

 

[fish_4_all]

Well this could help. My local lake is one that has been man made and was fairly deep 20 years ago. Being a man made lake, it has fish and lots of other animals and lots of plants. This lake does not get a lot of silt fill. Over the past 15-20 years, the lake has gotten 2-10 feet shallower. Why would this happen when most lakes don't do this? This lake has one outlet that is one of the deeper parts of the lake. All the plants convert energy into plant material. The material builds up after it dies off. The fish waste is converted into plant food and used. The other animals leave their waste and the plants use it also. As the plants grow, they deposit their own soil type material that is basically a sludge. This sludge builds up and the level raises slowly but shurely. This buildup leads to massive algae blooms that I have seen on lakes that are huge because the nutrients are so high that other plants thrive, like algae. The algae causes low level of oxygen and fish death.

Prime example. I have a 55 gallon I used to have set up and didn't know to do water changes. The gravel slowly built up the refuse from the fish waste and the plants, I had lots of different plants. After 3 years of the tank running great and never losing a fish to disease or some definate reason I got an algae bloom overnight that was thich as pea soup and killed everything but 2 groumis. After changing the water several times and getting the water clear it happend 11 times in the next month blooming overnight each time to levels that were horendous.

No matter what you have set in your tank there is going to be material that isn't used by the fish or plants and turns into a biomass. By removing the biomass the system can maintain it's normal cycle and not have to compete with the ever changing levels of "sludge" that would normally be removed by winter storms washing the lake bottom clean. Even rivers go through this. Low water in the summer lets sludge, slime and algae grow uncontrolled. The winter high water wipes the rocks clean for the cycle to start all over again. If this didn't happen, the rocks would be mud and no fish would ever be able to spawn in a river.

Nature renews itself all the time and water changes are our way of renewing the substrate and the cycle to keep things in balance.

 

[fish_4_all]

Just one other comment. The space station has to have waste dumps every so often, wether into space or into a craft that brings it back to earth. A biosphere that is self ocntained even on the planet has to have things brought in and things taken out in order to maintain it. I don't know if there is a new record but the longest sustained biosphere on the planet was only 9 years and then the biosphere actually started to become toxic to the inhabitants. Why, the best i could understand was that there was more waste than could be converted into energy and into something non-toxic.

I think the main thing to remember is that perameters change every day in a tank as they do in any biosphere. Getting things set up and running perfect can be done and will last a long time but once the conditions become extreme enough in any way it will eventually fail.

 

[TomK2]

Its a closed life- support system. Agaiin I refeer to the space station as a analogy.

your tank is not a closed system. You replace evaporative water, and you import nutrients (feed the fish). while many have tried to make the maintenance free tank, none have succeeded on a home scale. No matter what, you have to put food in. A heavily planted tank with very, very, few fish may be able to go the longest without an intervention, it will never be maintenance free. Ask yourself, am I providing the best conditions for my pets? No water changes might not kill your pets but it won't be the best for them.

edit: Oh no! I replied before I noticed there were five pages to this thread! I have now contributed to keeping a silly thread at the top instead of allowing it to fade into obscurity. Please forgive.

 

[Skyrmir]

Yeah it's a terrible thing to keep this going even longer. However, a thought occured to me. Would an RO/DI filter be able to clean tank water and remove the need for water changes? Thinking along the lines of taking old tank water and filtering it down to pure H2O. Of course it would have to be done slowly, something like that continuously would wipe out plant ferts, lower the KH etc. Maybe a timed cycle thing that would just run for an hour once a week.

More to the point, how much of a 'water treatment plant in a box' would you need to turn used tank water, into new tank water?

 

[scarf]

I don't know nearly the same as the people here but maths is a strong point so I thought I might give a lay opinion.

The crux of your argument is that with a balanced system, everything will be fine. That is true, but you must look at the different weighting on each of the variables in the equation. Since the system is "balanced", if one variable is increased on one side, the corresponding variable on the other side must be matched.

For example, if 5 + 2x = y
If x = 1, y = 7.
However, if x = 5, y = 15

I think the main idea is that the equation doesn't balance most of the time. Most of the time, the level of inputs (ie waste), will never balance with carbs and O2. Due to the imbalance, excess DOC will hurt your fish.

An analogy, imagine you lived in a fully sealed glass cube. You are continually pumped with CO2 from an exhaust, but have trees and other flora to "balance" it out. Although (simply) CO2 + plant life = O2, the flora cannot convert fast enough the CO2 (waste) to O2 ("clean" water), building up the CO2, until it becomes toxic.

This also applies to why, for eg, 10 neon tetras in a 20g tank will need less PWC than 10 goldfish in a 20g.

 

[Hara]

I have split off the water change posts and they are now located in the Freshwater general discussion area. I am also locking this post and if anyone feels this really warrants discussion, they can start a new topic.