Old Tank Water

[DaveA76]

is there anything beneficial to cycling in old tank water, as just starting fry tank rack up for malawi babies and ive always thought that its the filter that needs to cycle but just been told that old tank water 50/50 will kick start it,
ps the tanks will all be running on sponge filters
 

 

[Byron]

Generally speaking, no, you will not cycle with old water.  There can be other benefits though, in your case.
 
Nitrifying bacteria live on surfaces covered by water.  They adhere to what is termed a biofilm, which is a sticky substance that holds bacteria, microscopic creatures, algae, etc.  This is why transferring filter media or the entire filter is useful.  With the water flow, there will usually (but not always) be more bacteria on filter media.  If you could run the sponge filter in the main tank for a few days, it would likely be partially colonized with bacteria.
 
As for the other benefits.  If you are moving eggs or fry, or fish in general as to a hospital tank, using some or all of the "old" tank's water can lessen the shock caused by differing parameters and biological chemistry.  When dealing with healthy and mature fish, given all the "bad" stuff in the water it can be more detrimental than beneficial.
 
So in your case, as you are intending to transfer fry, I would use all water from the old tank and after the fry are transferred, do partial water changes but maintain close parameters (GH, pH, temp).
 
Byron.

 

[DaveA76]

thanks for that is ive always done a full cycle to get filters going properly, but this person said this which made me wonder if id been doing it wron all these years, as the water i was taking out is mainly to reduce nitrates

 

[TwoTankAmin]

I have always done a 50/50 mix old tank and new water when moving fry. But my tap and tank water stay pretty close in parameters to the extent I can add water directly to tanks from the tap. Its well water so I do not use dechlor etc.
 
To jump start the new tank. Rinse out your current media in the new tank with the sponges running. When the water has cleared (and it will fairly fast), add 1 ppm of ammonia to the new tank. When you have 0/0 for ammonia and nitrite, repeat that amount again. When you get 0/0 this time you should be fine to move the fry. You can do a 100% wc on the new tank first and put in 50% new and 50% old tank water. I am assuming you are not trying to stick 100 angel fry into a 10 gal. tank here.
 
My guess is the first new tank or two can be ready in a week to ten days from squeezing depending on how big the big tanks is and how well stocked.