Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Using the slow release materials are fine. You can also plant the tank while you are doing the fishless cycle. The plants are part of the bio cycle.
Some plants do not like that much ammonia. If something dies, remove it and try it again after the cycle is done.
If you are heavily planting the tank you may not even need to do a full fishless cycle.
a) The nitrifying bacteria are already living on the leaves and stems.
b) The plants are the biofilter, and the tank may not need a very big population of bacteria (see a)
Start the tank, plant it and add ammonia to 5 ppm. Test for ammonia, nitrite and nitrate in the first few days. If you find the ammonia is gone overnight even on the first day, and nitrite never shows up you have a 'silent cycle'. The plants are doing so much of the work that your tank can handle fish right away.
On the other hand, watch out using garden soil. It can work really well in an aquarium, but the microorganisms in the soil need several weeks to adjust to underwater living. If you see 'weird' readings of ammonia or anything else, then do not add fish. Continue with the fishless cycle. Some soils add so much ammonia to the water that you do not have to add any for the first couple of weeks. Toward the end the soil is releasing less ammonia and the bacteria are getting really good at removing it and may starve as the soil runs out of ammonia, so think about adding some ammonia if needed.