I had almost no sides at all during my test-e and dbol cycle. Barely blew up from the water retention and my nipples were fine. All I got was some slight acne that faded away in days. I see no reason to run an Aromatase inhibitor (AI) but might look into anti-prolactin.
I do always have nolvadex on hand might any estrogen related sides pop up
Tren is a 19-nor. 19-nor's act on the progesterone receptor and can affect progesterone levels. Also through what is possibly an indirect mechanism, they might also raise your prolactin levels. Look up the sides of these two things, they are NOT desirable at all. Estrogen can exacerbate these problems exponentially and I believe I've seen evidence that prolactin and progesterone increase the sides of estrogen in the other direction. Nolvadex will treat any gyno issues for sure but will do nothing for the high levels of estrogen still present even when taking nolvadex. So while you may not get gyno if you use nolvadex you may still end up with "tren dick" high blood pressure, loss of libido, etc. there is absolutely no reason not to use an Aromatase inhibitor (AI) whenever running an aromatizable compound unless you have blood work showing otherwise.
KingPen, BigKit, and MustangDX all said it, USE AN AI!