Help!

[OldMan47]

Water change amounts are not governed by any schedule. Instead they are dependent on the chemistry of your tank. If stocking is low enough, you can cycle a tank quite nicely with very few large changes and only a few small ones, as Mike says he did. If you have followed typical fish shop advice on tank stocking, you will have far too many fish to be quite that easy going about water changes. You will be doing much larger and more frequent changes. If you temperature match the water and use an effective dechlorinator, there is no reason not to do a 95% water change when needed. The bacteria that we are growing live on filter surfaces and not in the water, so a water change does not disturb them at all. In my own case, I clone filters using mature media and often have a filter ready in less than a week. If I mess up and stock a tank before its filter is ready, I do daily water changes where I drain the tank until the fish are having a hard time finding enough water to swim in and refill with freshly dechlorinated tap water. The end result is my filter finishes cycling rather quickly and the fish are never exposed to harsh chemical environments. Every time I do one of my giant water changes, my fish in the tank perk right up. Instead of stressing them, they act as if I have given them a tonic.

 

[waterdrop]

OldMan47 has stated this quite nicely. Its quite important for our beginners to grasp the full flexibility of the water change skill, from massive to small. There is absolutely nothing wrong with massive water changes when a few basic tenents are followed: Basic temperature matching should be observed (your hand is easily good enough for matching with the couple of degrees necessary), lowered chlorine/chloramine risk should be observed (young tanks under 6 months should ideally receive a 1.5x to 2x dose of a good conditioner to handle the off chance that the water authority has picked this fortnight to overload their system with anti-bacterial chlorine products) and "old-tank-syndrome" should have been ruled out ("Old-tank-syndrome" refers to rare cases such as when someone obtains a hand-me-down tank that has not had proper water changing, sometimes for years, and the fish have acclimated to excessively high heavy-metal and mineral content. A sudden large water change in these rare cases can be fatal.) Avoiding ever having "old-tank-syndrome" in any of your own tanks is an obvious reason for good weekly water-changing habits once you have fish.

It is also a fallacy that the two species of beneficial bacteria needed in a biofilter need to see toxic levels of measured ammonia or nitrite in the tank water in order to develop properly. Even good liquid-reagent based test kits will not register trace results at the lowest levels of ammonia and nitrite. Test kits will still read zero ppm even when enough ammonia and nitrite is cycling in the tank to maintain a healthy bacterial colony. This of course is the normal state for a healthy cycled filter. So during a fish-in cycle, there is food for the bacteria even when the test kits are reading zero ppm. And even during a very well done fish-in cycle there will be traces of ammonia and nitrite showing on tests prior to water changes, stimulating the bacteria even a bit more. So the name of the game in fish-in cycling is to deliver a non-toxic environment to your fish. That means not letting ammonia or nitrite(NO2) exceed 0.25ppm test levels!

~~waterdrop~~