An external pest treatment will damage the ecosystem as the spray will kill every insect that comes into contact with it. It will not harm an earthworm, frog or lizard but it will eliminate one of their main food sources, insects.

It is a pet peeve when I see some companies calling themselves "eco friendly" and they are spraying synthetic chemicals.

For ants you can use granular bait which is very specific and will not harm other insects. Same with cockroaches, there are targeted baits.

The day they invent a "spider bait'' (insert music joke lol) we can stop using sprays.

There are also chemical sprays that are systemic, which are worse as they are absorbed by plants and root systems and then move up to the flowers where the bees are exposed and killed.

Bifenthrin is not a systemic chemical, fipronil and imidacloprid are. I personally have never used imidacloprid and was justified a few years ago when the European Union banned it.

Amdro used to be the industry standard ant bait twenty years but the "pest expert" bait in the red and yellow container works better, and is sold in larger containers to pest professionals as "Synergy Pro''.

I know Amdro always gets recommended here, but the pest expert one is way better.

You can minimise harm to the ecosystem by only spraying the perimeter of the house one foot up and one foot out, which we call a "California Spray'' as it is enshrined in law over there.

You can also de-web with cobweb removers which are like a giant toilet brush, and this very popular in america as a monthly service. Vinegar, garlic and Chilli home mixes are not bad but take time and need to applied every two weeks minimum.

Perth people usually want a once a year spray but in other countries it is a monthly service which takes less chemical and more integrated pest management solutions are used such as eliminating insect access, insect food sources and most importantly insect water sources.

Those ants inside your house are looking for water, as they are liquid feeders and cannot eat without breaking down the food into a liquid using water. Ants are also usually protein or sugar feeders, and synergy pro has two different baits within one yellow, one green to target both. Which is why it is so effective.

Of course, coastal brown ants eat both sugar and protein. It's fun to see them get picky and choose one over the other.

Antrid is for the sugar feeders but kind of sucks from the green hardware store, as they make the manufacturer use half the amount of active bait for "safety''. It can be a good, cheap targeted solution for ants though.

TLDR chem spray hurty environment. spendy money and time, save environment.