There is nothing essential-to-life about cycled tank water...

[Sk8r]

...except it has bacteria, and that totally replacing a tank's water would weaken its processing ability. Back in the day, we used to cycle a new tank with absolutely dead rock and sand by buying a gallon (usually given free) of used tank water from the lfs. We learned later this can bring you a few things you'd rather not have, but just understand that tank water has life in it.

Is it essential? You could keep a very bored marine fish in nothing but brand new salt water in a bare glass box SO LONG AS you keep changing that filter pad out every time you spot a brown stain on it (white side out.) This is exactly what you may do if you run a no-cycle qt. Which is my preference. But it goes through a lot of filter pad.

Why you should know this---? If you have a tank disaster and need to move a fish or such to safety, do not waste valuable time trying to put together a cycled tank. Good water is quite enough. You just need to be stain-conscious and keep it scrupulously clean, ie, PREVENTING A CYCLE which can kill your fish. YOu're kind of stuck with that program until your regular tank calms down, but you'll be fine so long as your blue-white filter pad supply holds out and you keep conditions pure and clean.

 

[JohnZena]

...except it has bacteria, and that totally replacing a tank's water would weaken its processing ability. Back in the day, we used to cycle a new tank with absolutely dead rock and sand by buying a gallon (usually given free) of used tank water from the lfs. We learned later this can bring you a few things you'd rather not have, but just understand that tank water has life in it.

Is it essential? You could keep a very bored marine fish in nothing but brand new salt water in a bare glass box SO LONG AS you keep changing that filter pad out every time you spot a brown stain on it (white side out.) This is exactly what you may do if you run a no-cycle qt. Which is my preference. But it goes through a lot of filter pad.

Why you should know this---? If you have a tank disaster and need to move a fish or such to safety, do not waste valuable time trying to put together a cycled tank. Good water is quite enough. You just need to be stain-conscious and keep it scrupulously clean, ie, PREVENTING A CYCLE which can kill your fish. YOu're kind of stuck with that program until your regular tank calms down, but you'll be fine so long as your blue-white filter pad supply holds out and you keep conditions pure and clean.

Thanks Sk8r, that is valuable info, especially for a newbe such as myself.

Sent from my LGMP450 using Tapatalk

 

[Sk8r]

And how can absolutely pure water develop bacteria? the question you may wonder. There's a live fish pooping into the water. That's where. So be careful not to have leftover food: feed just enough; and watch that filter pad for bacterial activity, and you'll be fine.

 

[mcgyvr]

Bacteria is virtually EVERYWHERE...

 

[JZinCO]

Why you should know this---? If you have a tank disaster and need to move a fish or such to safety, do not waste valuable time trying to put together a cycled tank. Good water is quite enough. You just need to be stain-conscious and keep it scrupulously clean, ie, PREVENTING A CYCLE which can kill your fish. YOu're kind of stuck with that program until your regular tank calms down, but you'll be fine so long as your blue-white filter pad supply holds out and you keep conditions pure and clean.

Preventing a cycle? Just to clarify for myself and others, because when I think of 'cycle' I'm referring to the transformations of nitrogen through nitrogenous compounds from A to Z (I guess technically it's linear and not a cycle in our glass boxes), you specifically mean Urea and excrements into ammonia, correct?

And I'm fairly surprised that you can remove enough waste quickly in order to prevent sufficient transformation into ammonia. But kudos to you! I've never tried to do that. If one can hinder ammonia build up through frequent filter changes, one wouldn't need to change QT water on a very frequent basis. I would much rather change filters more frequently if that meant less water changes in a QT.
My new build is going to have a 'cycled' QT tank setup 24/7 but you gave me something to think about.

 

[Sk8r]

Basically, the cycle PRODUCES ammonia, and bacteria that can eat it multiply. If you can stop the production of ammonia by keeping it scrupulously clean---no ammonia, no problem. Ammonia is fatal to fish in very small doses. [Not so much to corals, ironically. But conversely, corals die of nitrate, which fish tolerate at truly awful levels.]

Anyway, yes, clean water is healthy for fish. Once you let food and poo produce (through bacterial action) ammonia, it's bad for the fish. So long as you just keep refreshing that filter at any hint of bacterial activity, you're good. You could keep a whole FOWLR tank this way if you were prepared to keep switching filters to an entirely unreasonable extent. Since this is not practical, and since canister filters even on a cycled tank build up a big charge of nasty for the bacteria, then toss it all, canister-maintained tanks are boom and bust for the bacteria, and for water quality---which is why they don't do well for corals, which do relish fish poo.