Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Moving or redoing a tank with Fish and Bacteria
1) Set up new water ahead of time if needed. I use garbage cans. Add dechlor, minerals, peat... whatever is needed to make the water ready for the fish. Make sure this water is the right temperature. (An aquarium heater can be suspended in a garbage can)
2) Put some water from the tank into buckets for the fish. Cover the buckets with the fish. Fish jump. Separate buckets for separate species, or aggressive fish. Loaches separate. Stressed Loaches can produce excess slime coat that seems to kill other species in small volumes of water. Keep the beneficial bacteria alive in the filter, and on the decorations by keeping these things damp. The bacteria does not need to be covered in water. It does need high humidity and oxygen.
3) Remove old substrate. You could skim the top 1/2" and set that aside separate from the rest.
4) Set up tank, decor, substrate, a few inches of water... then PLANT. Mist the plants a lot.
5) Fill the tank with mostly new water. You could use some reserved water, but it is not necessary if you have followed my step 1. Put a plate or plastic bag over the substrate and run the water in slowly so it seeps into the substrate. This will reduce cloudiness. Put the reserved 1/2" of old substrate into mesh bags and hang it where there is good water movement. This is the part of the substrate that is richest in bacteria.
6) When it is time to add the fish, DO NOT use the water from their bucket(s). Stressed fish produce more ammonia and stress hormones. You do not want these in the new tank.
Best ways to keep the nitrifying bacteria:
Keep most of the decor, the upper layer of substrate and old filter when you change the substrate. If you can add more plants, especially fast growing ones that will help, too.
If you know ahead of time that you will be (possibly) killing off some bacteria you can grow more yourself in a bucket. Set up a fishless cycle using any sort of pump or bubbler to keep the water moving, and add some bio media, or even a sponge. Anything the bacteria will grow on. Add ammonia, and follow the fishless cycle until the bio media is rich in bacteria. (Takes about 3 weeks) Then add this to the filter or just hang it in the tank where there is good water movement.
Live plants are a very good biological filter. Live plants need good light to be efficient filters.
Add Dr. Tim's One and Only or Tetra Safe Start to the tank. These and certain other products contain Nitrospira species of bacteria. Read the label, and do not waste your money on anything else.