Predator insects are important as they help to maintain a balance in the garden; therefore it is important to make sure that you keep predator insects alive by being careful not to use artificial fertilisers. There are already fewer predator insects in most gardens then there used to be due to a variety of different issues therefore it will take them much longer to recover if something should happen to them.
If you do not keep enough of these types of insects around then the pests will recover and soon enough your garden will get out of control or ruined by them. There are many commercial liquid feeds that have too many nitrates in them that you really need to watch out for. These type of feeds will promote growth and while the sappy growths will look nice at first, they o not really help your plants are actually unhealthy for them in the long run.
On the other hand, a slow release fertiliser is a much better option and will help to preserve your garden for a longer length of time. You also should think about good garden compost methods because there is no reason not to produce great compost and make your own fertilizer.
In order to make compost tea from your own compost, simply take an old bucket that has a lid and fill it about a third with rotted garden compost and then top off the bucket with water. Place the lid on and let it sit for two to three weeks until the compost has fermented and you can see gas bubbles sitting on top of the water. At this point the water will be laced with the compost making it the perfect liquid feed to poor back over your garden!