How can I keep my lawn thick and green with no fleas or ticks?

See if these help you:

https://weedmanusa.com/news/seven-tips-healthy-lawn

https://www.familyhandyman.com/landscaping/lawn-care/how-to-achieve-a-healthy-lawn/

https://www.thisoldhouse.com/ideas/9-steps-to-lush-lawn

https://www.popularmechanics.com/home/lawn-garden/how-to/g863/6-simple-tips-to-get-rid-of-ticks/

https://pesthacks.com/how-to-get-rid-of-ticks-in-your-yard/

https://www.domyown.com/how-to-get-rid-of-ticks-a-489.html

There are a number of cheaper fertilizers on the market and if you try something like 8-8-8 lawn fertilizer, which is a granule, then you will notice a difference. Be sure to follow the instructions on the bag.

I've been using nematodes and have been very successful, especially with the fleas, my dogs are smail so their flea magnets. I sprayed the lawn this spring and it 's lush and tick/flea free so far. https://www.google.com/search?q=nematodes+for+ticks&oq=nematotdes&aqs=chrome.2.69i57j0l5.5376j0j4&sourceid=chrome&ie=UTF-8

Adding nematodes....Use Beneficial Nematodes to Control Grubs, Fungus Gnats,Fleas and Over 200 Other Soil Developing Pests! ARBICO'sBeneficial Nematodes are live microscopic organisms (non-segmented round worms) that occur naturally in soils throughout the world. https://www.arbico-organics.com/category/Flea-and-tick-control ----over seeding lawns helps keep weeds from growing do not cut grass shorter/more than 3"s water well early in day so it doesn't get fungal disease from being too wet. apply maure/compost everyother year to add needed nutrients,healthy soil is needed to grow healthy grass. stay away from chemical fertilzers and do not over apply them if you choose them creates problems unhealthy soil that creates unhealthy grass.