There Is Allot Of Argument

[TigerLotus]

I don't think I could say I believe a tank(any size) could go without a change ever. I do believe in pretty heavily planted, moderately stocked tank it can go for an extended(as in years) period of time without water changes, only top-offs.

Tiger Lotus

 

[MarkByrom]

this is true my 280 gal get's changed once a year, and thats on 20 %.

However it does look like i've robbed a rainforest with the amount of shrubbage in there.

MB

 

[tenohfive]

NOT TRUE WHATSOEVER. Fish need fresh water to survive. Also, if you were rasiing baby fish, they owuld only get so big, becasue they let off growth hormones. Once there are to many growth hormones, they stop growing. Also, how would a 300g tank be any different form a 30g bsdies it has more room for mistakes, and takes longer for nitrate to build up?

dont agree tbh.

my koi pond has been running for about 5 years or so.

we flush the filters out and at most loose about 50 gallons. im alwas told for koi mature water is better. rain water is bad as it has lots of unfilterd pollutants where as tap was has chlorine which helps remove them and then put though a water purifier to remove the chlorine and other rubbish

Koi are extremely hardy, and your water is still mature, you still have bacteria and everything. Our rain water isnt polluted, becasue i looked into it with some sort of water society and i also asked my Earth Club teacher and she said they tested it a couple years ago adn supposedly its not that bad. I've used rain water before in tanks with no side effects, and would do it again if we got a substantial amount of rain to use in a water change. I have also tested it for nitrates and everytihng and we have 0 ammonia, 0 nitrites,m and 5 nitrates. And water dosent get very mature, becasue there isnt much if any Beneficial bacteria in it, all the bacteria is in miniscule crevices in the rocks, filter pads, and just about everywhere else.

Your rainwater might not be heavily polluted where you live. That doesn't mean everywhere else is the same. Elsewhere, it does contain pollutants.

 

[MHunt]

Any fish system could get away without water changes if you can complete the nitrogen cycle. I believe that's the case with marine tanks, as with the use of live rock and magic mud systems the nitrate is also removed from the water. This is much more difficult to achieve in a fresh water system which is why we all do regular water changes. That said even when the cycle is complete there are probably other organic by products that cannot be removed from the water and the only way to remove them is by water changes. The advantage of a system as large as 300 gal is any build up is going to be so slow that you can probably get away without doing any water changes for long periods of time.

 

[Evad]

For what its worth, I have had 200 gallon tanks that were fully planted and lightly stocked - and I used to do water changes about once every 3 months at 40%. At one point I went almost 6 months just to see what would happen, and the tank did show signs of degrading after the 5th month. I would say that having a big tank is only part of the potential to not do frequent water changes. You need to have it fully planted to absorb and recycle nutrients and waste. You also need it lightly stock with fish that are not particularly sensitive to water conditions.

But why go through such hoops to avoid a water change? If anyone is hoping they can find a way to eliminate water changes, perhaps they should select a new hobby, like dogs.... No, wait. You would have to change the water bowl. My bad!