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Ammonia from Waste (poop) vs Ammonia from food


Socqua
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I've been thinking about this a lot and would love either anecdotal feedback or scientific evidence, the latter being preferred of course...

Everyone is always talking about a cleanup crew, be it corydoras, plecos, snails, shrimp, etc. The idea being that when you feed your "main" fish, the leftovers that they don't get will be picked by the scavengers, leading to a cleaner tank. Of course some critters clean up better than others, and some also leave waste better than others, but in as general terms as possible are cleanup crews really worth it?

Another way of asking this: Is the ammonia (and other byproducts) from fish poop/waste less than the ammonia from the food needed to feed those scavengers? Or, if you didn't have snails/shrimp (that you often have to feed extra to anyway, but I digress), would the tank really be dirtier than if you just fed a little less/had a little leftover food buildup? (By dirtier I mean needing more frequent water changes due to nitrate buildup etc.)

I think this not a simple question with a simple answer and I know I didn't cover all the nuances here, but hopefully we can have a little discussion!

 

Edited by Socqua
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I'm not sure, I suppose I'd start by looking up Urea. I'd think that if something is eaten, at least some of it is absorbed by the fish as weight. Then urea comes out. However as hobbyists we may overfeed with more fish added negating the little benefit we get by a fish eating it vs it rotting. I dunno.

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Me, I just love to watch snails and shrimp. They can be so cute and fun and surprisingly active, and are often found at the bottom of the tank where fish are in the top half. So "cleanup crew" is more like a convenient excuse. That said, they don't just clean up leftover food. Many of them also eat algae, dead plant material, and detrivores like snails will also break down fish poop. Some, like malaysian trumpet snails, have further benefits of keeping sandy substrates aerated.

Also, figuring out exactly how much to feed fish can be challenging. So a clean-up crew can help mitigate some of those errors. And, maybe I'm thinking a little simplistically about it, but the more digested a piece of food is, the less final waste there is in the end, right? Because some of that food goes to growing  your cory cat or your snail before the remainder gets excreted.

And some creatures, like shrimp, are supposedly more efficient eaters than others, with a very small nitrate footprint. So for each gram of food/waste they ingest, they may excrete less than other creatures.

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i think the "clean up crew" just gets it one more step closer to broken down.  that way the beneficial bacteria in the aquarium dont have to do the whole process themselves. no matter how it happens, if food goes in the aquarium, it eventually has to be broken down, so it is all a balance of how it is done and distributed.

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16 minutes ago, Cory said:

I'm not sure, I suppose I'd start by looking up Urea. I'd think that if something is eaten, at least some of it is absorbed by the fish as weight. Then urea comes out. However as hobbyists we may overfeed with more fish added negating the little benefit we get by a fish eating it vs it rotting. I dunno.

Thanks for the response Cory! Obviously I too do not know 😆.

I'll definitely do more research. I think the question boils down to: does adding a shrimp to scavenge food lower your nitrates after a week (or decrease the need for water changes)? And I think the answer is that even with a low bioload critter like a shrimp, they're going to be adding more ammonia than if they weren't there.

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10 minutes ago, Kirsten said:

Me, I just love to watch snails and shrimp

I agree. Certainly this isn't a "don't buy shrimp because they aren't actually beneficial" post... I love my shrimp and my nerites.

Very good points. On the point of algae-eating benefits: if you add a snail to get rid of algae, but then you have to do water changes more or feed more to make up for it, is it worth it? (That's supposed to be thought-provoking, not combative). Sure they get the nooks and crannies and plants, but maybe solve algae with less light/food/etc. and just occasionally manually clean the glass.

I don't know, maybe getting off my initial point and just thinking out loud now lol.

 

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5 minutes ago, Socqua said:

On the point of algae-eating benefits: if you add a snail to get rid of algae, but then you have to do water changes more or feed more to make up for it, is it worth it?

Eh, might be splitting hairs at that point. Maybe I understock my tanks, or have so many plants that they suck up all the nitrates they can get, but I haven't noticed an appreciable increase in nitrates in tanks after getting snails. Even big-time poopers like mystery snails have been no big deal for my ecosystem. But I know that algae on my plants was a huge problem. It choked them out and killed them and wouldn't go away even with cut-back feeding and lighting. Wasn't till I brought in small snails that they finally got clean.

And some of it comes down to enjoyment, too. I like being able to keep my aquarium lights on for 12 hours or more so I can enjoy them for longer in the evening. I like to watch my fish eat, so I like to feed them (lightly) twice a day without worrying about measuring super precisely. While I might chuck a piece of celery or cucumber in for my snails every once in awhile, they mostly make do on excess food and any algae growth from the lighting. So I think a clean-up crew is just one further enrichment of the ecosystem of a tank, breaking waste down one step further and mostly subsisting on scraps and cleaning up my miscalculations (ooh, and messy eaters who might just take a single chomp, then let the rest fall). Not 100% vital for a successful tank, but still a good idea.

Sure, you could just have a single betta in a bare bowl, feed it very sparingly and carefully, keep the lights down low, and have to change the water just about as much as an active, brightly lit tank full of plants and animals. But you could also put a glass of water on a countertop and never have to change it! 😄

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All organic waste is decomposing to become relatively inert. Scavengers merely help accelerate the process so that facultative bacteria can finish the job. The scavengers are truly beneficial and there are creatures in your substrate bio-filter that boggle the mind (see How Microscopic Hunters Get Their Lunch)

With less stock and or less feeding, there will likely be less waste...and in general, less waste is always good as it results in better water quality between partial water changes.

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I think the answer is no there is no practical difference in a typical community tank. 

 

As others have pointed out nitrogen goes to biomass of fish while they're growing.  If your fish/shrimp/snails are full grown though that means they excrete in one form or another as much mass as they take in.

As far as i can tell animals don't excrete nitrogen in any form that's lower energy than ammonia so the majority of whats excreted eventually ends up as ammonia (through urea mostly).

Anything growing/reproducing like "pest" snails and shrimp will though as some fraction of their biomass is nitrogen.  Humans are about 3% nitrogen.  other animals are not as easy to google.  Assuming a guppy is the same, my 100mg guppy then is 3mg Nitrogen which is the equivalent to sinking about 3-4mg of ammonia or 1ppm in a gallon of water.

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Interesting question. I think that the term "clean up crew" is open to some interpretation here. What do we mean by clean? After all they aren't called "ammonia reducing crew." I think they do a decent job at turning turds into mulm and keeping certain algae manageable. I also kind of feel like the term is used as a sales tactic, because I don't know many people that have thought my bristle nose pleco is attractive or that don't say my shrimp remind them of bugs.

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This is really fascinating. Initially I thought of this from a closed system--your input (food) mustt equal output (waste) minus the amount used to grow or maintain the animal.

In most cases this is negligible, as @CT_ points out, meaning food in=waste out--UNLESS something is reproducing. From a nitrogen/ammonia standpoint that means your best cleanup crew, that actually result in a net drop of in tank waste, are shrimp, snails, and duckweed--If you remove the excess animals/plants, without letting them die in the tank and release their sequestered nitrogen (it is in the amino acids that make up protein).

You exchange water changes for population control. There ain't no free lunch...

Or is there? A perfect micro-ecosystem would make it's own food out of the waste... 😏

 

 

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40 minutes ago, Brandy said:

You exchange water changes for population control. There ain't no free lunch...

I've been reading about what the "no water change" crowd does because its really interesting.  in addition to plant clippings and animals out they run deep substrate so that anaerobic denitrifying bacteria release N2, which leaves into the atmosphere!  pretty neat.

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3 hours ago, Aubrey said:

I think that the term "clean up crew" is open to some interpretation here. What do we mean by clean? After all they aren't called "ammonia reducing crew."

That's a good point. I think most experienced fishkeepers understand that adding a bristle nose pleco doesn't make for a cleaner tank, if by clean you mean healthy (I mean even that name isn't "attractive"... Bristle.. 👃... Pleco, I like em though). But, for those less experienced, something that cleans up gross algae (even if it turns it into poop) might seem like it makes a healthier tank, maybe needing fewer water changes.

 

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