It depends. Limestone rock is good for many purposes. If thick enough it will help reduce rooted weed growth. It helps with alkalinity (reduces pH fluctuations). It is great as a place for craws to forage and live . In the right location it will help survival of bottom spawned fish yoy ( BG/LMB/RES etc). It helps with many microorganisms growth as it contains Ca which is essential. If you have high alkalinity you may not want to add more. It is very tough on bare feet.