Phemex will be a good choice for trading major cryptocurrencies. Right now, there aren't many assets available (for example, XRP is missing due to registration with FinCEN), and the trading pairs are mostly based on USDT. So it's not surprising that most trading is concentrated on the BTC/USDT pair, which accounts for about 90% of the total volume. The ETH pair is also actively traded. The other assets are less liquid than one would hope. In conclusion, if you prefer altcoins, it's better to look for another exchange. If you're mainly interested in the classics, then welcome — the conditions are quite acceptable.
