beechey -- She isn't that big. Probably undersized for her age, she's about 15 cm long, and I bought her in 1994 or 1995. For various reasons (not least being out of the country for several years) she has had to make do with a variety of less than optimal aquaria, at best ~45 gallons. That's much less than this species really needs. That might have had a stunting effect. I also don't feed her that much, basically she gets wood most of the time, and algae wafers and vegetables two or three times a week. No high protein foods (like mussel) at all. On the flip side, she's obviously healthy and happy.
Bex -- I assume the high protein issue is the same as with humans. We have a taste for foods that "in the wild" are scarce -- fat, sugar, and salt. We don't binge on stuff that's abundant, like vegetables, fruit, and water. So in the wild our ancestors would gorge on the rare stuff when they found it, because they "knew" it wouldn't always be there. Now we have farming and mass food production, we still eat those fatty, sugary, salty foods because we're hard wired to do so. Our bodies "think" they should store these foods as insurance for when they're not around, so we get deposits of fat around the organs and under the skin. In the wild, these would never last for long, because they'd be used up regularly, but in modern times, they just sit there. The end result is that fat around the internal organs causes damage to the organs, interferes with blood flow, and so on. Result: diabetes, high blood pressure, heart disease, etc.
I have to assume the same is true with plecs. A Panque normally eats wood, but in the wild, a dead fish or a patch of insect larvae would be a rare treat. It would gorge on the stuff, because it mightn't get another chance for weeks or months. In the wild it couldn't overeat because for whatever reason it wouldn't often find that food. So it normally makes do with wood. In the aquarium, it doesn't know not to eat too much, and if provided with protein and fat rich foods, like meat or catfish pellets, it eats them as long as they are there, probably in preferance to wood. End result: the Panaque equivalent of heart disease and kidney failure.
Funny story (and something for you to look forward to). Yesterday I cut some cucumber for the Panaque, stuck some lead weight into it, and popped it in the aquarium. As it happens, I didn't use enough lead, and the food floated. My Panaque swam out and up to the top of the tank, where she forced the cucumber against the glass. Within an hour or so, she had dragged the cucumber into her burrow under the sand, where the food couldn't float away!
There are really nice fish. Mine has given me years of pleasure, and it's rare to find a plec that is both hardy and colourful. Enjoy your fish!
Cheers,
Neale