Yep, I noted same in my initial comment.
In commercial dog food one will typically see feeding suggestions such as the following in a quality puppy food: Metabolizable energy is 4000 kcal/kg (520 kcal per 250ml/120g cup) - while the same brand has the following on one of their Fit & Trim formulas; Metabolizable Energy is 3530 kcal/kg (425 kcal per 250ml/120g cup)
The big difference between dogs & fish is, some dogs can & will manage their own intake, I currently own a dog like this, others, if allowed, will eat until they are almost sick. I have also owned dogs such as the latter. The vast majority of tropical fish fall into the latter scenario, where most, if allowed, will eat until they are ready to explode.
LOL when you mentioned 'exploding' I thought of one of my parrots in particular, BOSS. I would say my Oscar and two of my parrots metabolize "higher". They would have to eat
massive amounts of food to get fat (caveat one lays crazy eggs and all are still growing). The other two parrots gain weight quickly with only a moderate amount of food. My most massive parrot BOSS will balloon quickly if I don't monitor his eating. He's the only 'bottomless pit.' Very slow to slim down as well.
To no surprise the most active fish also maintain their weight better.
So:
KONG (bp), PATCH* (bp), BRICK (O) - maintain weight with moderate feeding. PATCH gets more to compensate for the crazy egg output every 2 weeks. KONG sometimes bulks out but loses it quickly with less food.
TANGO (bp) Gains weight quickly but loses it relatively quick based on feeding.
BOSS (bp) Gains weight quickly but loses it very slowly based on feeding.
CASH (Syno) maintains no matter feeding.
So it seems I have 4 high metabolism fish, 1 moderate metabolism fish, and 1 low metabolism fish.