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So I target feed them each night with a pipe until their enthusiasm fades, and that's usually a palm-full of pellets, pill bugs, etc. They are plenty full at bedtime. Nevertheless, I've noticed a disturbing lack of Oscar turds since I moved the trio into this tank. Should I feed their bloated bellies even more? I know they are more tolerant of nitrates as a species. Is this why? For poop digestion?

*is slightly confused*

Cich-lids have a fast, but messy digestion track. I think the oscar poo contained sufficiently nutricion for the Platydoras - and therefore your tank will remain cleaner than it used to be

in 1988 I had a problem with the substrate in my cich-lid tank - it needed more handling, so to say. I got 3 Platydoras and thinking about it, I never fed them - they just ate what they found, and as they are still swimming, and doing will, i think, it was a good enough 'diet'

It's true that the Oscar waste looks only partially digested, often being composed largely of still-whole pellets. I just always believed the 'experts' who told me that no fish eats waste.

It is untrue that no fish eat waste; Scatophagus are named because they have been observed eating fish waste. However, I would never recommend nor rely on fish to clean up fish waste.

Actually, I don't think there's a commonly used term that includes a -vore ending. I searched and found very few hits for coprivore, and no hits for scativore and fecivore. However, the phenomenon of feeding on feces is called "coprophagy", which is analogous to saying carnivory and herbivory.

Many fish will eat ANYTHING that contains any nutrition - most live in conditions where food is scarce - at least during certain times of the year.

I think the "fish don't eat other fishes waste" is not at all correct, but at the same time, it's wrong to "buy fish to eat the waste of other fish", for two reasons: Most people don't understand that the fish that eats other fish's waste will also need fresh food, and most people don't understand that if you put more fish in the tank, you need to change the water more often - even if it doesn't look dirty!

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Mats

most people don't understand that if you put more fish in the tank, you need to change the water more often - even if it doesn't look dirty!

That still amazes me. To this day I can ask most hobbyists I meet from craigslist how their nitrates and pH are and they'll have no clue. So I gently hint at better husbandry methods, but it's hard to do without getting rude, and I need these people.
I hope 'educated' fishkeeping keeps spreading. I mean, if I can find out what's right for my fish, anybody can.

MatsP wrote:Many fish will eat ANYTHING that contains any nutrition - most live in conditions where food is scarce - at least during certain times of the year.

I think the "fish don't eat other fishes waste" is not at all correct, but at the same time, it's wrong to "buy fish to eat the waste of other fish", for two reasons: Most people don't understand that the fish that eats other fish's waste will also need fresh food, and most people don't understand that if you put more fish in the tank, you need to change the water more often - even if it doesn't look dirty!

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Mats

Actually, I think I disagree with you, Mats this time

If I have a fish which only digests its food partially, I add 20 nitrogen, in order to feed it say 15. the other 5 will eventually spoil the water, just as the earlier 15

Whether these 5 nitrogen are eaten by another fish, or not, in both cases all the 20 nitrogen will end up as nitrate - which will have to be remouved.

Fishfood will have to be digested, if not, it will attract fungus, or snails or whatever. Personally I think a fish which performs a secondairy digestion, together with sifting out uneaten particles, is a very good addition to any tank

In other tanks I have sand sifting cich-lids. I don't have any illusions about what they eat - semi digested fishfood will be a large quantity of their diet.

However, I do agree with you that these fish ALSO need some fresh food

Bas,

I'm not at all disagreeing with you - I certainly agree that any nitrogenous (ie. protein) food put in will eventually turn into nitrogenous waste in the form of nitrate (assuming correctly working biological filtration). All I'm saying is that there is a reason that many people there is a good reason that some people say "fish don't eat waste", and if the aquarist is not experienced and understand the matters at hand, buying fish with the intention of "clearing up the mess" is not the right thing to do.

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Mats

Mats

You are right pointing out people wil lread along with our discussions, and we should keep in mind suggestions - which work in a certain situation - might turn out bad in others.

And re-reading my previous post, I admit it can be construed as defending feeding fish with nothing but waste. I did not intent to say so, but I could have pointed that out much more clearly

I have a feeling that what is happening is at night the Platydorus are merely breaking up the Oscar's formerly conspicuous feces and the smaller particles then are more easily picked up by your filter.

I have kept some fish which actually habitually eat other fishes feces.
Ctenochaetus hawaiiensis and Ctenochaetus strigosus will follow other, larger fish and "recycle" their wastes. That is why I nicknamed them, Hawaiian S**T Eaters.
Very useful fish in a reef tank that handles many of the same chores we expect of our common Bushy Nose Plecos. Take a look at one. Very attractive for fish having such diverse utility. The most commonly seen species is C. strigosus, Yellow Eye or Kole Tang because they cost about 20% as much as the C. hawaiiensis. I have kept one or the other of these species in every reef tank I have ever had.
http://animal-world.com/encyclo/marine/ ... hevron.php