What Percentage Of Water Should You Change When Your Aquarium Has Fini

[Wansui]

- shed Its cycle? ( sorry for long title) I ask this because on the cycling guide it just says "do a large water change" well... how much? 50%? 75%? more? I would be greatful if someone could enlighten me.

 

[eaglesaquarium]

As large as possible. 90+%.

 

[ShinySideUp]

All of it, right down to the substrate, as near as dammit competely empty; you want no stray ammonia knocking around in there.
 
Empty it, fill it up, bring it back to temperature while leaving alone for 24 hours, then fully stock with fish; this is how I did my last fishless cycle and it worked perfectly. There was no ammonia spike, all the fish were healthy and survived to have full lifespans. Many of them are still going; my Clown loaches for example have long lifespans and are now into their 10th year after my fishless cycle.

 

[yinyangpete]

I didn't read the guide, so I'm in no way qualified to interpret the phrase "large water change."
 
However, at the end of the cycling process, you should not be seeing significant amounts of either ammonia or nitrites.
 
After your cycle has completed, the goal of water changes is to reduce nitrAtes.

 

[eaglesaquarium]

I didn't read the guide, so I'm in no way qualified to interpret the phrase "large water change."
 
However, at the end of the cycling process, you should not be seeing significant amounts of either ammonia or nitrites.
 
After your cycle has completed, the goal of water changes is to reduce nitrAtes.

 
 
This is correct.

 

[TwoTankAmin]

Since I wrote it, it means at least 50% and 75% would be fine and more will not hurt. But the idea is to remove anything that has built up from or for the cycle. The most obvious would be nitrate. But TDS may have built up, pH and KH may have dropped. If one has used baking soda to hold up parameters, there is a need to remove the sodium.
 
Basically, the idea is to start the fish off in nice clean water at the parameters in which it will be living. Clearly there should be 0 ammonia and nitrite in the water once a tank is cycled. But there may be other things you do not want. So it is always better to be safe than sorry.