Using ammonia in a fishless cycle

[irishspy]

If the point is to grow bacteria that eat ammonia and assuming the cycle goes well, why is it recommended to do an 80% water change once the cycle is finished? Haven't the ammonia and nitrites been converted by then?

 

[msjinkzd]

i believe its to reduce the nitrates

 

[Sploke]

Yes...when you finish cycling, all that ammonia you added has been converted to nitrates. When I fishless-cycled my reef tank, my nitrates were at like 160 at the end. It took a few large water changes to bring them down to acceptable levels before I could start adding fish.

 

[irishspy]

i believe its to reduce the nitrates

Ah, that makes sense. T'anks.

 

[southpaw]

Yup...You do it to get nitrate levels down as alot of times they will be 100+ and you need to get them down around the 20ppm or so range to be safe for the fish you stock.

 

[jm1212]

less than 20 ppm is preferable, especially since it is a new tank without any fish. get the nitrates as low as possible, doing 90% or more water changes if you have to.