Keeping mine in a 55g. He started as a 1.5-2" lil fella to about 6" killer. He stopped tolerating his established tankmates at about the 3.5-4" size and killed several, the ones who survived his destruction live in a 29g now.
Surprisingly he's somewhat accepting of 3xConvicts females 1.5-2" in size. VEry curious about a 3" Pike i added, but the (bellycrawler i think)Pike gets out of the Grammodes way as best it can. He does get close to biting the con's, he could easily bite one in half. I got them as target fish.
The longest tankmates i've kept with my Grammodes so far are 2 Clown Pleco's. He was very curious about them the first 2 months in the 55g. Not so much now.
My grammodes before i added the convicts and Pike was still a lil skittish. He's out more now but