Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Here is what I would do:
Keep the shrimp in the tank, add plants, and do enough water changes to keep the ammonia barely reading at all. As close to 0 ppm as possible.
In a separate container do the fishless cycle.
For example, in a 5 gallon bucket, put whatever filter media will fit in your filter, and a small fountain pump or a bubbler or anything that will keep the water moving really well. I would keep the media in the current filter running on the tank, hoping for any sort of recovery that will help the tank. If the media in the current filter has any bacteria at all the shrimp will need it.
Follow the fishless cycle in that container, not the tank.
Start with 5 ppm ammonia until the nitrite shows up, then allow it to drop to 3 ppm until the cycle is done.
For the tank, go get a bottle that contains Nitrospira species of bacteria. This is the exact species that you need to repopulate the tank. Use it according to the label directions for the tank, and if you have some left over you can jump start the fishless cycle that is going on in the bucket. That way you are hopefully growing the bacteria in 2 ways, in 2 places. If there is a 'crop failure' in the tank, you have the back up of more bacteria growing in the bucket.