I'd go with the Severn Trent value. They have to get their water tested several times a year and they know exactly what is going down the pipes to your postcode.
Plants.
The idea behind cycling is that fish excrete ammonia which is toxic to them. Cycling is the term we use for growing bacteria which eat the ammonia, and another set of bacteria which eat the nitrite that the first lot make from the ammonia. When enough of these bacteria have grown, they keep the tank safe for fish.
Plants take up ammonia as fertiliser and they don't turn it into nitrite. If there are enough fast growing plants, the take up all the ammonia made by a tankful of fish, and keep the fish safe.
So to keep the fish safe we need to do one or the other.
Plants do need a bit of work. They need fertiliser - plants need more than just ammonia; like garden plants they often need pruning. Some plants are classed as easy, some as difficult and some in between. The difficult plants tend to be harder to keep as they need extra things like carbon dioxide added to the tank, so stick with easy plants to start. Look for the plant company Tropica on-line, and look for their easy plant list.
Floating plants are good for two reasons. They take up more ammonia than lower down plants and they shade the fish. Most of the fish we buy come from waters with overhanging vegetation so they like having something over their heads.
As for plant cycling, with this method you set up and plant the tank then wait till the plants show definite signs of growth. the last thing you want is to get fish then all the plants die. Once the plants are growing well, you buy the first batch of fish and test for ammonia and nitrite every day. if they both read zero, great. If they read above zero, you need to do water changes to get them down. Once you've had zeros for a couple of weeks, you buy the next batch of fish.
This method depends on there being enough plants. Just one or two slow growing plants sin't enough, but something like water sprite or frogbit flaoting on the water will go a long way towards being enough.
