blueacara said:
Hey thanks a lot for all the advise then I shall be doing a 50% water change every 2 weeks.
It would be very much better to do a water change every week at minimum, rather than every two weeks. So, although the more volume that is changed the better, doing 25% every week rather than 50% every two weeks will be much improved for the fish and the aquarium.
I will explain why a bit. Water in an aquarium "pollutes" very rapidly [I'll come back to "pollutes" momentarily]. When we do a water change, we remove a portion of the polluted water, but the remaining water is obviously still polluted, so by the next water change the pollution has actually increased because the same amount is being added every day/week but we are not removing all of it. The more water you can change, up to about 60-70%, the better. For example, a 70% water change once a week is much more effective than doing 10% every day. The aim is to remove as much at one time as you can, in order to reduce the build-up of pollutants. And whatever amount you change, the more frequent the better, and it should never be less than once every week. This actually works not only to remove the bad stuff, but it will maintain a better stability in water chemistry. The change in water conditions after one partial water change every two weeks will be much greater (and have more impact on the fish) than it will after more frequent changes.
"Pollutants" are many. Fish urinate a lot, it is how they rid their systems of all sorts of things like excess minerals, salts, solids (TDS or total dissolved solids), and just old water. Fish cannot "drink" but they take in water continually through their cells, and this has to be processed and expelled. They also release pheromones and allomones, which are chemical substances that other fish "read," and these can only be removed by changing water, not with any filtration. The solid waste can be broken down by bacteria and/or trapped in the filter, but as it decomposes it releases substances that accumulate in the water, and some of these remain regardless of filtration.
A comment on water conditioners. These are rather expensive, but there are some methods to save money. First, make sure you are not using more than necessary. Almost every manufacturer will recommend more than is required, and say it will not harm the fish; while the latter aspect may or may not be true depending, there is no point in adding more chemicals to an aquarium that what is absolutely necessary. And when it comes to water conditioners, adding sufficient for the volume of water actually changed is all you need.
Second, some conditioners are less expensive than others. Compare how much you need for each brand (they usually say "x" amount for 10 gallons or something) and the cost. Also, the conditioner only needs to deal with whatever is in the source water; stuff like chlorine, chloramine, metals, ammonia, etc. And, sometimes you can buy them online, and in larger sizes, and this can save a lot of money long-term.
Byron.