Crypto tax question

Can someone help a noob out on crypto taxes?

Suppose I bought 1 ETH at $500 and sold it at $600 for BTC. I'm suppose to pay taxes on my gains from ETH ($100).

What if I immediately sell back the BTC for the ETH again with no price changes on either tokens. Basically I made neither a gain or loss on this trade. I simply converted the tokens. But now I have less ETH than when I started. Is this right?