chem and cycling new tank

I'm new to this forum and to marine tanks. I do have extensive experience with fresh water tanks. I have set up my tank about 3 weeks ago - cycling with live sand and rock. I had, as suggested by the place where I bought the system, purchased a couple damsels which died just about a week later. I have been testing daily - ammonia level stays at 0.25, nitrite 0, nitrate - small amt - which i think is a bit backward as I believe ammonia goes up, then starts down as nitrite starts up, then that starts going down as nitrate goes up, which then eventually drops to 0 and the tank is cycled. ph, alkalinity and salinity have all been measuring fine. My question is - this tank doesn't seem to be cycling. The ammonia level isn't going up - I hate to put damsels in there just to watch them die. I do have a couple bettas - one of which I have to add epsom salts to his water changes as he seems to have a problem with constipation (didn't know that could happen with fish!!) Was wondering if I could save the water from the other betta tank from water changes
- make it into salt water - and add that to my marine tank to help get it started to cycle? any suggestions?
Thanks

 

Fresh water bacteria and Saltwater bacteria are not the same. It will usually take 6-8 weeks to fully cycle your tank. Just be patient it will happen.

 

some use a shrimp to get cycling. just a raw one from the store should do it

 

Hi I use Ammonium Chloride to cycle, and I can drag it out as long as I wish. And I am assured the correct bacteria is formed so minimising other's which do more harm than good, later on when all is matured. Regards.