I have been seeing a lot of people throwing around the term soft cycle when referring to how they plan to start their tanks or as to how they are cycling their tank. Unfortunately most don't grasp the true meaning of a soft cycle and just jump on the bandwagon, as with so many other things in reefing. Hopefully I can clear a few things up.
The concept of soft cycling is simple, to keep as many sessile inverts and plants already on the rock alive during the cycling process by keeping the ammonia at a minimum. The key to a good soft cycle is high quality, fresh live rock, good lighting on a regular cycle, strong filtration (skimmer and running carbon are sometime necessary), regular water testing and very frequent water changes. Before you even think of soft cycling a tank you need to make sure you have the resources at your disposal to correctly soft cycle a tank. Do you have the money for high quality rock? Do you have a place to get the rock from? Do you have accurate test kits for NH3/NH4, NO3, NO2? Do you have plenty of salt and water on hand for water changes? Do you have enough storage space to store premixed salt water for water changes (sometimes as large as a 100%)? Do you have enough time to do daily water changes, test the water, monitor the tank, empty skimmer cups for up to 3 weeks? If you answered "No" to any of these a soft cycle is probably not right for you.
For those of you who did answer "Yes" to all the questions lets go over what preparation should be done for a soft cycle. The most important part of a soft cycle is the quality of the rock you start with since you can only maintain the animals that initially come in on the rock. A lot of people on this site I have seen claiming to soft cycle their tanks using very white or drab rock with almost no life, this entirely defeats the purpose of a soft cycle. The best way to get high quality live rock is to find a local store that can get direct shipments from importers or, even better, directly from the source in the eastern pacific or the Caribbean. Learn when they are expecting a shipment and have your tank ready before it arrives to minimize the amount of time that the rock remains out of water. If a local source can not be located then you can always get live rock from one of the many online sources, I would highly recommend Premium Aquatics. Call them and learn when they are expecting a shipment from a source that is known to typically have high quality live rock covered in life. Next set-up a shipment so that as soon as they get it they turn around and ship it to you. The most important thing about getting live rock shipped to you that it is shipped Overnight; Express or Ground WILL NOT WORK. It is vital that transfer time is kept to a minimal.
Once you get the live rock it is important to go over it thoroughly before you add it to your tank. Remove any dead crabs, worms, sponges, etc. from the rock. Determine which face of the live rock is up and identify where potential corals are and make sure they are facing towards the light. I would also leave as much macro algae, even potential pests, on the rock as possible as they can metabolize a significant amount of free nitrogen and carbon into their tissue. Its best to point strong flow going parallel across the face of the live rock so as to remove as much debris as possible and get it into the water column where it can be removed mechanically or neutralized chemically. Skimming is also going to be to be crucial to success (at least IMO) as it is perhaps the easiest method to remove dissolved organics from the water column. Remember to tune your skimmer to maximize the amount of skimmate that is pulling, keeping a constant watch to ensure the skimmer is running as efficiently as possible.
Now comes the hard part, keeping as little nitrogen in the water as possible. Nitrogen in the form of ammonia and nitrite will readily burn many of the animals that are intended to be saved by a soft cycle. The water in the tank must be monitored constantly and appropriate action must be taken based on these results. Water should be tested once if not two or three times daily. During the first couple days you should expect to see a spike in ammonia and large water changes (between 50-100%) should be preformed according to test results. It is important to set-up a water standard as far as temp, salinity, PH and alk are concerned and adhering to these standards for any new water entering the tank, so as not to shock the animals any further. Testing should continue and water changes done accordingly until nitrATES are registering near zero for a few day. There is absolutely no time table that can be set for a soft cycle as it is largely dependent on you filtration system, quality of live rock, and time spent in transit.
I hope this is helpful and I will readily edit it as need be.
To be continued.......