When we need to set up a Hospital Tank for a sick fish we often don't have much warning. The priority is getting the tank set up and ready for fish ASAP. We don't have time to properly cycle the tank. Since we will likely be dosing medicines into the tank, we can't use live rock. One of the most important things we can do to minimize ammonia levels is to only feed what the fish will quickly eat and remove any uneaten food quickly. This is the ounce of prevention. The fish will also naturally produce ammonia, so what other options do we have? Regular water changes to keep ammonia down is one option. This can not only be expensive and time consuming but it also makes maintaining the correct level of medicines challenging. If you are a good Cub Scout and are always prepared, you probably keep a sponge for your HT's HOB filter in your sump. Shame on me, I don't, so this isn't an option. This is actually a very good idea since it is the most reliable way to add nitrifying bacteria to your HT. My preference is adding a store bought product of nitrifying bacteria, commonly referred to as Bacteria in a Bottle. This can be a quick way to establish a large enough population of nitrifying bacteria to prevent ammonia build up with a light biological load in your HT. It is important to remember that nitrifying bacteria do not typically live in the water column. They prefer hard surfaces to cling to. Having a media with a lot of surface area will be very useful to sustain a healthy population of bacteria. This can be filter floss, a sponge, or other specialized media. Just try to chose one that will not absorb medicines or copper. So we have set up our HT, put some filter floss in the HOB and we grab our bottle of bacteria and dump it in. We are good to go, right? Well, not necessarily. Not all bottled bacteria products are the same. They fall into 2 major categories. They can be active (or live) which means as soon as you add them into your aquarium they go to work. They can also be inert and in a spore form. These bacterial will need more time before they will efficiently process ammonia. You may also notice that some claim to contain aerobic and anaerobic bacteria. For use in a HT only the aerobic bacteria are important. Anaerobic bacteria are used deep in live rock or in a deep sand bad to convert nitrate to nitrogen gas. This won't happen in a properly set up HT. If you need a tank set up, and set up now, using a live bacteria product is going to be the best way to go. It will make a noticeable impact within a few hours of adding it. The live bacteria products do have some drawbacks. First, they have a shorter shelf life. They are typically full strength for up to 6 months and will still work well for up to 1 year. The product will also need be stored at room temperature or refrigerated. If it is frozen or exposed to too high a temperature it is likely that enough bacteria will be killed to make the product useless. The bacteria that come in a spore or cyst form may not work well for a day or 2. If you need immediate results you may be disappointed. The nice thing about these products is that they are very stable. They can be frozen and handle relatively high temperatures much better than live bacteria. They also have a shelf life of 5 years or more. It isn't too uncommon to find a bottle of live bacteria that doesn't work. That is much less likely with these products. If you have 2 or 3 days to get your filter established prior to adding fish, this is the way to go. Just remember, you do need a small ammonia source to get these bacteria functioning at peak levels a few days prior to adding the fish. A few drops of pure ammonia or a little ghost feeding should get this bacteria going. So which products are which? Some are pretty clear and some take a bit more research. In my next post on this thread I will put a list of what category each product fits in. I will try to keep it updated. If you are curious about a product you don't see on the list, please let me know and I will see if I can research it and find out. Edit: I wanted to throw out another suggestion which I did when I set up my QT the latest time. In addition to using Biospira I also added some macroalgae into my QT. (Thanks for reminding me, @beaslbob ) As long as you start with a clean and copper free QT this is an excellent way to help control ammonia while your bacteria population grows. Just remember to pull it out prior to treating with copper or other medicines that could kill the algae.