Failure to change water frequently allows the accumulation of pollutants that will affect fish health and growth. So why do we have to change water? Basically for a few reasons:
1) supply fresh water to the fishes
2) removal of excess waste or food
3) removal of Nitrate and any presence of chemical
4) finally, water changes replenish elements and minerals in the water needed to maintain a healthy environment
in one of the message posted by ranchugirl, it was mentioned that frequent water change will introduce better fish growth.. another reason why you should change water more frequently.. the message can be found here - http://www.kokosgoldfish.com/forum/index.p...hl=water+change
anyway, I have noticed that many people stick to fixed rule by only changing 10 ?20 % of the water in their tank on a weekly basis. That?s a good practice but many people have failed to judge the condition before applying the rule. Many people also fail to understand that rule do not apply to every situation.
So what are the consideration factors to determine how often you should change water?
1) Fish Tank ratio ? How many fishes you have in a given tank. The more fishes you have in a tank will definitely produce more waste.
2) How often you feed your fishes ? this is another condition that varies in every people where some people chose to feed once while some people chose to feed twice or even more.
3) Amount of food fed - Some fish eats more than the others, which also contribute to the waste level
4) Plants ? the amount of plants you have in a tank will definitely affect the level of nitrAte. Loose leaves that are left in the tank will rot to produce ammonia too.
5) Water characteristic ? water from different water source will have different properties. Thus different water will have different level of tolerance.
Another thing to take note. Do you treat/age fresh water from the tap? Treat meaning to add any required additive to achieve the required condition where chlorine and chloramine are removed and PH greater than 7.0. Ageing of water is to leave the amount of water that you will be adding into the tank in a bucket overnight before pouring them into the tank. By leaving the water overnight, unnecessary gaseous and will be evaporate and encouraging absorption of oxygen. Adding an air stone is greatly encourage in this aspect but not necessary.
One more point, Topping up your tank does not constitute as water change! Water may evaporate but not the undesirable components (such as nitrAte) in it! Worse of all, as water evaporate, the concentration of the undesirable components will be higher (base on per gallon basis).
For those who may understand mathematics, I shall briefly put my understanding gained from reading here with some figures. Lets say your fish is giving out 20 nitrAte each day and you must keep it as low as possible though 0 is impossible. At 20 per day, it will be 140 in 7 days. By changing 50% water, you keep it down to 70 (week 1). Another 7 days have past that brings the nitrAte to 210 and by changing 50% of the water again, the nitrAte is down to 105 (week 2)! Starting to notice something? Another 7 days have past that bring the nitrAte to 245 and 50% change will bring nitrAte down to 123. Yes, despite changing water, nitrAte is still increasing. So many people are experiencing problem after a long while despite they stick to all the rules to ensure everything in perfect condition.
You may vary in your feeding with different kind of food in different amount and at different hours. What about water changes? Do you vary in water changing as well or still stick to the 10% -20% on weekly basis rule? See, so if you vary in feeding, then you have to vary your water-changing schedule too.
Another advantage of water changes that I would like to introduce, especially at time of crisis. When you notice your fishes are not acting normal, say staying at the bottom of the tank, does not eat, and even over turn! HELP!!
Relax, what would be the first thing you should do? Change part of the water will enhance the condition of the tank that will also makes your fish feel better. And most problems start off with bad water. NitrAte is a major culprit that contributes to many forms of infections (may it be external or internal). Especially internal infection, some organ may swell that cause it to narrow the air passageway thus affect its swim bladder (that?s why they over turn). Before the condition is worsen, change water and maintain water quality will definitely nurse the fish back to health. Especially for swim bladder cases. At most time, we can?t see what is going on internally. We can only assume the fish has recover when it starts eating or swimming. But unknowingly, the infection is still active within. But good water quality and good environment help the fish to nurse back to health.
Many times I have come across cases of fish problems that were solved almost immediately with water change. Where owners immediately see sign of improvement when their fishes started to behave more normal. If they have follow the advise to maintain the water quality, that might be the reason why they did not follow up with that thread anymore and they are still chatting happily away in the forum. That?s a good sign, for it goes to show that they have solved the problem! Am I right?
Therefore, I would like to encourage everyone to judge for him or herself and only you know yourself better. How often you should change water depends on the common factor mention above. Well, I think it has become my habit that I felt my main hobby is changing water and not keeping goldfish.