Are fish in tune with their dietry needs?

[esoxlucius]

Go anywhere near your tank and your fish go crazy, they want food, always begging. We hear the phrase "feast or famine" on here all the time. Fish will just gut load themselves because it's hard wired into them that they don't know when the next opportunity of food will present itself. This is all common knowledge amongst hobbyists. But.....

I have a red tailed giant gourami who is about 5 years old, so full grown. He is about 16-17" and quite thick. When he was younger he would eat like a pig, he'd eat anything, never wasted a morsel, and of course when he'd had his portion, which I felt was right for him, he'd still want more. At this point you just have to hold back, you can't overfeed them, you have to be responsible and do the right thing for the fish, not to mention your water parameters.

However, over the past 12 months or so i've noticed a dramatic downturn in his eating habits. He doesn't want as much, he spits food out after a while and nowadays it's a regular occurrence for him to totally refuse food that he once went crazy for. He isn't eating even a quarter of what he once ate. He can go a week, easily, without eating. Am I worried? A little maybe. He doesn't look undernourished, he doesn't look ill, he doesn't skulk about.

This got me thinking. Obviously a fish needs food to grow but once a fish reaches adulthood and it's max size does that "hard wiring" inside them change? My GG is a docile fish and so doesn't use a lot of energy. He doesn't need food to grow anymore and doesn't need food as an energy source, not much anyway. I suppose he just needs enough to survive.

Is it possible that adult fish have the awareness to do this? if so my GG is the perfect example of it. What I can't explain though is the fact that I know many of you will now give me details of your adult monster fish eating like pigs still with insatiable appetites. This scenario would then lead me back to the worrying thought that maybe there is indeed something wrong with him.

What are your thoughts?

 

[duanes]

I have also noticed a similar loss of edge with cichlids, when they get beyond what seems to be, reproductive viability, so this may go hand in hand with an abbreviated appetite..
Old males seem less robust in their energy to defend previously jealously guided territories.
In nature, in the Cenotes of Mexico I have watched "old" Rocio males (JDs) become relegated to less desirable areas by the young more virile males, and spend time simply hovering, like old scrapes in retirement homes.
Seems less awareness, than it simply being hard wired into them, that once the height of their reproductive prowess gets beyond a certain point, they settle to waiting for some cormorant to come along and put them out of their misery.
Small fish with a maximum life span of only a few years (less in nature when the predation factor is applied), might be almost moot,
but with larger species, a lifespan of 10 years or more is not out of range.
And in aquariums we have the ability to maintain life spans much beyond the norm (although predation from birds probably gets 3/4 of them before reaching reproductive maturity) of a natural life span.

Above, a Cenote populated by JDs above, below river edge in Colombia.

 

[tlindsey]

Go anywhere near your tank and your fish go crazy, they want food, always begging. We hear the phrase "feast or famine" on here all the time. Fish will just gut load themselves because it's hard wired into them that they don't know when the next opportunity of food will present itself. This is all common knowledge amongst hobbyists. But.....

I have a red tailed giant gourami who is about 5 years old, so full grown. He is about 16-17" and quite thick. When he was younger he would eat like a pig, he'd eat anything, never wasted a morsel, and of course when he'd had his portion, which I felt was right for him, he'd still want more. At this point you just have to hold back, you can't overfeed them, you have to be responsible and do the right thing for the fish, not to mention your water parameters.

However, over the past 12 months or so i've noticed a dramatic downturn in his eating habits. He doesn't want as much, he spits food out after a while and nowadays it's a regular occurrence for him to totally refuse food that he once went crazy for. He isn't eating even a quarter of what he once ate. He can go a week, easily, without eating. Am I worried? A little maybe. He doesn't look undernourished, he doesn't look ill, he doesn't skulk about.

This got me thinking. Obviously a fish needs food to grow but once a fish reaches adulthood and it's max size does that "hard wiring" inside them change? My GG is a docile fish and so doesn't use a lot of energy. He doesn't need food to grow anymore and doesn't need food as an energy source, not much anyway. I suppose he just needs enough to survive.

Is it possible that adult fish have the awareness to do this? if so my GG is the perfect example of it. What I can't explain though is the fact that I know many of you will now give me details of your adult monster fish eating like pigs still with insatiable appetites. This scenario would then lead me back to the worrying thought that maybe there is indeed something wrong with him.

What are your thoughts?

Only thing I can add is some species of fish when mature lose that voracious appetite.

 

[esoxlucius]

The timing of this thread couldn't have been better really. My GG was on one of his fasts, hadn't eaten since the middle of last week. Today when I came home from work I went to have a look at my 360g and he was there at the front shaking his head against the glass. I've come to recognise this as his give me food headshake.

He had a handful of chopped strawberries, a couple of raspberries, a few shrimp and algae wafers and a few medium sized hikari sinking pellets. I guarantee now he'll go about another week, maybe longer, before he asks for food again.

If full grown adult fish really don't need to be fed as often as we think, in theory that is great. Potentially a tank full of adult fish would only give out a minimal bio load. Interesting.