A grid bot's break-even spacing
Each grid level buys and later sells, so every completed cycle pays the fee twice. The gap between two levels has to be wider than that, or a filled cycle loses money.
On a Bitkub THB pair, at 0.25% each way, a cycle costs 0.50%, so levels closer than about 0.5% apart cannot make anything. On Binance the floor is about 0.20%, on WOO X 0.12% if both sides take, and on Bitfinex it is set by the spread alone.