What happens to the water?

Howdy Prof...I know that we all do water changes bcoz its the norm to do so,BUT why?What really happens to the water that our filters and conditioners cannot do that we have to remove it from our tank?And we do have goods like amrid/zeolite to reduce/remove ammonia or plants to utilise the nitrates.Can we store tank water and filter or polish or whatever in order to reuse????????????

 

Hi Fishcrazy;

I am sure that the Professor will answer your question as soon as he get's a chance. He is away at the moment, and may take some time to answer. I will however give you a very brief answer.

Fish waste, uneaten food and breaking down plant matter is broken down by bacteria into ammonia. Ammonia is broken down again to NitrItes. NitrItes is then broken down to NitrAtes. This is the basic Nitrogen cycle. It's called a cycle, because in a perfectly balanced system, the nitrAtes are then used as fertilizer by the plants. Plants decompose, some get's eaten... and so the cycle begins again.

Unfortunately our tanks are not a static system... There are many different changes... plant load and fish load being the 2 most common changes... but no one really takes into consideration that if you overfeed, or even underfeed your fish, your load will change.

Yes, the plants will use up the nitrAtes, but as far as I know, they will only use what they need. There is no other way to take the nitrAtes out... except through water changes. Hence the 10-15% waterchanges that are recommended as a bare minimum.

I have however seen a few tanks (even on this forum) where members actually DO NOT do waterchanges for months at a time. You will however find in that circumstance that they have a fairly LOW fish load, and a fairly HIGH plant load.

 

You get denitrifying filters aswell.

The big reason is that it is simply cheaper to do water changes to remove nitrates and other unwanted substances than to buy and run all the other equipment and trace element suppliments etc. That is also the reason why marine tanks use loads more of equipment to ensure water quality with fewer water changes, when you start using RO water and need to add synthetic salt etc it get more expensive to do water changes and thats why all the extra equipment is run on marine tanks, some marine tanks only get a 20% water change once every month or two.

For example to do a fresh water change would cost you R0.20 per liter (with water treatment etc). Where as producing RO water, adding salt etc will cost you R2 per liter.

 

I've personally run tanks for 6 months at a time without water changes, but these were special cases with blackwater-loving fish and a high plant load and extremely good filtration for the size of tank.

However what has been stated above is true, the main problem is that trace elements are not being placed back into the system and most planted aquariums still do not have enough capacity to remove all nitrates.