The octopus will hunt and eat them, so you can remove it from the aquarium after a while and you will have an undesired specimens - free system in which you may now introduce the animals and invertebrates you want. Plant fertilizer packages usually refer to a dose which is considered as the optimum one. Use this exact dose when you are sure that no excess of other nutrients is present in your aquarium water. These nutrients have a close relationship with the bio load and the amounts of food you feed i.e. the more you feed the more nutrients are already in your water, therefore the less fertilizer you will need. Usually fish jump out at dawn or twilight.
Many cichlids are great jumpers too.
Use covers in your tanks when you introduce new fish for about the first week. They prefer low to moderate level of light. They are sensitive to light, temperature and water conditions changes though. They are prone to cryptocoryne leaf disease. They love fast moving water, so it is better to be planted near the current of a filter or water pump outlet.