100% Water Change, Is A Cycle Needed?

[Fluval-1200]

As per title, ive just drained my tank to remove leaking bulkheads.
My sand and filter still have old water in to keep the bacteria going, but when I refill the tank with fresh water will it need to be cycled again?

 

[zoopkamol]

nope should be ok.

 

[misterpro]

Not unless your filter has been starved of food/oxygen for very long.

 

[daveg6529]

Providing your filter bacteria is ok & you reuse your substrate there should be no problem and no need to recycle.

 

[eaglesaquarium]

The bacteria live on SURFACES not in the water... so assuming that this tank was cycled before the water change, that dechlorinated water was returned and that you didn't do anything 'silly' to the surfaces where the bacteria live, then it should all be just fine.
 
 
It is a myth that the water is where the bacteria 'live'.  Some bacteria can be 'washed off' the surfaces on a rare occasion, and they will then float around until they can adhere to a new surface - which is how they arrived in your tank in the first place - but this is a VERY SMALL percentage compared to what's in your filter, substrate, etc.  If there is any loss of the bacteria, the remaining bacteria can easily multiply to make up for that loss in a matter of a few hours.

 

[Fluval-1200]

ideal thanks for the info