Cycle As Freshwater then Convert?

[picoreeflexguy]

I want to begin cycling a new reef tank today, however, I will be going out of town for 3 weeks and do not yet have an auto top-off system in place. I do not plan to put any fish/inverts/live rock/ etc in it right now but live sand, so my question is if I have an ammonia source in the tank, should I cycle it with proper salinity knowing water will evaporate over the three weeks and the SG will rise or can I cycle it as freshwater then add salt to make it marine when I return and can have a proper setup in place? I really want the tank to be cycling while I am gone so open to any suggestions. 

 

Thanks 

[jahnje]

I'd think it would be best to add the salt and ammonia now, cover it, and let it sit while you're gone.  If there's nothing in it then the evaporation probably won't really matter.  Just fill it back up when you return. If you we're planning on live rock, now would probably be a great time as well. 

 

 

[fishkeepersaltnfresh]

I would cycle with the saltwater instead of freshwater.  I have not heard about any adverse affects on tank cycle due to increase in salinity due to evaporation.

If you are concerned about evaporation , then I would not put in a heater and would also cover the top of the tank.

Hope this helps.

[picoreeflexguy]

1 minute ago, jahnje said:

I'd think it would be best to add the salt and ammonia now, cover it, and let it sit while you're gone.  If there's nothing in it then the evaporation probably won't really matter.  Just fill it back up when you return. If you we're planning on live rock, now would probably be a great time as well. 

 

 

The live rock wouldn't be affected by the increase in salinity? Thats the only reason I am foregoing right now. Thanks

[picoreeflexguy]

1 minute ago, fishkeepersaltnfresh said:

I would cycle with the saltwater instead of freshwater.  I have not heard about any adverse affects on tank cycle due to increase in salinity due to evaporation.

If you are concerned about evaporation , then I would not put in a heater and would also cover the top of the tank.

Hope this helps.

Thanks for the info. My only concern with no heater is the temp in the room could cause the temp in the tank to be in the 50s or 60s, which may be to cold for bacteria growth?

[jahnje]

5 minutes ago, picoreeflexguy said:

Thanks for the info. My only concern with no heater is the temp in the room could cause the temp in the tank to be in the 50s or 60s, which may be to cold for bacteria growth?

W/o a heater in the tank there's a good chance that would slow down the cycle.   You never said the size of your tank, but if you cover it you're really not going to lose that much water and I'm under the impression that liverock really wouldn't be affected anyway. But I do think if you don't have a heater in the tank you're going to come back and find that the cycle hasn't really gotten very far.  Unless it's freezing, the bacteria should still grow, albeit more slowly.