Water Change Frequency

[CFC]

Nitrates are not the only reason to change water, along with nitrogen compounds there are also organic proteins (dissolved organic solids) which build up and can play havock with the pH as they release acids into the water and encourage blue green algea. There are also essential minerals which keep the water chemistry stable which need to be replenished regularly as they are used up as a bi effect of the nitrogen cycle, without them the pH can crash litterally over night, and a unstable pH is one of the biggest killers of aquarium fish.

On tanks with low stocking levels and decent filtration you can get away with bi weekly water changes but community tanks or those with large or carnivorous fish a weekly water change of a minimum of 10% is highly benefitial.

 

[dwarfgourami]

Talking about high nitrates, I also think it makes a difference whether nitrates are high because of tap water or creeping up because you rarely do water changes. In other words- what's going to happen when you do change the water, will it be a gentle shift or a big shock? I have heard of tanks that have been neglected over a long period of time, and where a sudden water change has then sent the fish into shock.

Anyway, leaving off the water changes isn't really an option for me: I have fry in all my tanks now and poor water is known to affect their growth rates. Also, my corys need a clean bacteria-free substrate.