I ran a triangle trading arbitrage bot on Coinbase that was profitable at the end of 2017. But a few weeks later, it was losing money on hard to diagnose slippage. The number of “opportunities” also collapsed, which indicates that other bots were doing the same or that coinbase was doing this internally.

I pulled the plug. Tried to run it on Binance but the websocket only updated once a second, so there was way too much risk.