Crangonyx as an algae eater

[dw1305]

Hi all,

There must even be quite a lot of them if I can always see them but I've still never once seen a baby or intermediate size crangonyx other than when I introduced the original 12 which were a mixture of different sizes. @dw1305 do you also find that the small ones remain completely hidden until they are adults? or do you also see them swimming around?

All sizes swim about, which is probably why they don't tend to last with any micro-predators, however small.

There's a really ridiculous amount of palces for them to hide between loose gravel and heavily drilled lava rock so based on the fact I can always usually see at least four scooting about I assume there's probably dozens living in there by now but despite really looking I've seen them mating but not a baby even once.

Try a bit of cooked vegetable, something with some colour (Green bean would be ideal), and all sizes will probably accumulate on it.

cheers Darrel

 

[louis_last]

Hi all,

All sizes swim about, which is probably why they don't tend to last with any micro-predators, however small.

Try a bit of cooked vegetable, something with some colour (Green bean would be ideal), and all sizes will probably accumulate on it.

cheers Darrel

It's a bit of a puzzle because I feel like they must be breeding based on how many I can see. It would be easy to believe that all the babies are getting eaten but if cherry shrimp manage to survive I would assume some crangonyx could too. I wonder if it might be to do with flow, I never really see the adults swimming just scooting over rocks, maybe the flow is causing the babies to hide deeper in the gravel but I also wonder if they're small enough when they hatch that they essentially have a floating planktonic phase and that's when the fish are getting them.My sundanio definitely totally ignore the adults.
Seems the only food that gets a reaction out of them is bacter ae, they ignore my diy gel food and other commercial pellets but they seem to get a lot more active when I feed some bacter ae just like the other shrimp.

 

[dw1305]

Hi all,

Seems the only food that gets a reaction out of them is bacter ae, they ignore my diy gel food and other commercial pellets but they seem to get a lot more active when I feed some bacter ae just like the other shrimp.

They like cucumber.



Cheers Darrel

 

[ScareCrow]

I think they may also eat black beard algae. I was going to post back in the summer but didn't have an opportunity to test if it was Asellus or Crangonyx that ate the black beard algae. The container I placed the black beard algae covered plants contained both species. After a few days the black beard algae had been completed removed from the plants though.

 

[louis_last]

I think they may also eat black beard algae. I was going to post back in the summer but didn't have an opportunity to test if it was Asellus or Crangonyx that ate the black beard algae. The container I placed the black beard algae covered plants contained both species. After a few days the black beard algae had been completed removed from the plants though.

I think it's the asellus. I have seen them eating BBA but not in the same quantities or at the same pace as hyalella azteca seem able too. There's also references to them being effective algae eaters, and consuming BBA, on russian language fish forums. I've seen this specifically referenced on here before and a russian friend confirmed and showed me some links a while back. I'm not sure why they aren't more popular in aquariums but I suppose it's because you don't see them much. I introduced several at the same time I added crangonyx to my tank and I have seen one once in the same period that the crangonyx have either multiplied or become bold enough that I can see them scooting about almost all the time.

 

[dw1305]

Hi all,

I'm not sure why they aren't more popular in aquariums but I suppose it's because you don't see them much.

I really like them, in some ways they are the <"perfect tank janitor">. They are more active at night, and don't swim in the water column, but possibly just because they <"lack aesthetic appeal">?

I introduced several at the same time I added crangonyx to my tank and I have seen one once in the same period that the crangonyx have either multiplied or become bold enough that I can see them scooting about almost all the time.

I think the "scooting bit" is why Crangonyx <"don't persist with most fish">, but Asellus do.

cheers Darrel

 

[louis_last]

I think the "scooting bit" is why Crangonyx <"don't persist with most fish">, but Asellus do.

cheers Darrel

It's still a bit of a puzzle to me given that H. azteca are widely known to become problematic pests even in tanks fairly well stocked with fish and they are only very marginally larger than crangonyx. I've seen people report that H. azteca are quite responsive to the presence of fish predators and that they will change their behaviour in the presence of fish to hide more in the substrate etc.
When I was keeping the crangonyx in a large glass jar they spent most of their time clinging to the glass eating biofilm but now they're in the tank I have never seen one anywhere other than substrate level and this may represent something similar but there's too many variables to tell.
I'm still certain that my axelrodi totally ignore the adults even when they swim past their faces but they may well be eating the babies. I'm just hoping that enough can hide wherever the cherry shrimp do to maintain a population.

 

[louis_last]

I really like them, in some ways they are the <"perfect tank janitor">. They are more active at night, and don't swim in the water column, but possibly just because they <"lack aesthetic appeal">?

Agreed. They have different colour morphs of Asellus in Russia just like we do cherry shrimp. Maybe you should try a bit of selective breeding?

 

[dw1305]

Hi all,

It's still a bit of a puzzle to me given that H. azteca are widely known to become problematic pests even in tanks fairly well stocked with fish and they are only very marginally larger than crangonyx.

<"I've never kept"> Hyalella azteca - <"https://fishtankdk.blogspot.com/2013/01/live-food-hyalella-azteca-breeding-and.html">, but it would be an interesting comparison. I wonder if H. azteca are just a lot "crunchier", and that this might put some fish off?

I've seen studies looking at the interaction of other amphipods and Crangonyx sp. and it looks like Crangonyx are eaten by pretty much all the other Gammarus, Dikerogammarus etc sp., so I'm guessing you couldn't keep Hyalella and Crangonyx as a mixed culture, whereas I know that Asellus aquaticus and Crangonyx pseudogracilis can co-exist without any problems <"Predators vs. alien: differential biotic resistance to an invasive species by two resident predators">.

When I was keeping the crangonyx in a large glass jar they spent most of their time clinging to the glass eating biofilm but now they're in the tank I have never seen one anywhere other than substrate level and this may represent something similar but there's too many variables to tell.

I'd guess that is just <"where the food is">?

They have different colour morphs of Asellus in Russia just like we do cherry shrimp.

I've found out that they do lab. genetic work on colour morphs, so they maybe available more widely. This is a useful paper for Asellus diet etc. <"Frontiers | Building on 150 Years of Knowledge: The Freshwater Isopod Asellus aquaticus as an Integrative Eco-Evolutionary Model System">.

This one has some details for Crangonyx <"https://www.sciencedirect.com/science/article/pii/S1470160X2100025X"> "Leaf breakdown rates as a functional indicator were influenced by an invasive non-native invertebrate in urban ponds"

cheers Darrel

 

[dw1305]

Hi all,

I think they may also eat black beard algae. I was going to post back in the summer but didn't have an opportunity to test if it was Asellus or Crangonyx that ate the black beard algae.

@Konsa found that Asellus eat BBA in <"Feeding a California Blackworm culture - Lumbriculus variegatus">.

I don't tend to have <"much BBA"> in the tanks, but I have a lot of different tank janitors, so "cause and effect" are difficult to pin down.

cheers Darrel

 

[LMuhlen]

How would one be able to acquire some of the animals mentioned in this topic, or others similar, in a distant country, say.... Brazil, as an example?

 

[dw1305]

Hi all,

How would one be able to acquire some of the animals mentioned in this topic, or others similar, in a distant country, say.... Brazil

Probably tricky for Asellus or Crangonyx spp., your best bet might be a University? Where they are interested in water quality?

Some Hyalella spp. are native to S. America <"https://www.tandfonline.com/doi/full/10.1080/01650521.2021.1964902">, so that maybe another option?

A further option would be to pyo by netting a local small weedy stream (or pond) and then trying to identify any crustaceans you find. This one could be very interesting, but leaves you open to collecting something <"monstrously carnivorous"> - <"Macrobrachium amazonicum - Wikipedia">.

cheers Darrel

 

[louis_last]

How would one be able to acquire some of the animals mentioned in this topic, or others similar, in a distant country, say.... Brazil, as an example?

we would probably kill to get our hands on whatever fills a comparable ecological niche in brazil! you must get out there with a net and let us know what you find!

 

[louis_last]

Hi all,

<"I've never kept"> Hyalella azteca - <"https://fishtankdk.blogspot.com/2013/01/live-food-hyalella-azteca-breeding-and.html">, but it would be an interesting comparison. I wonder if H. azteca are just a lot "crunchier", and that this might put some fish off?

They defnitely look crunchier. The crangonyx are a lot more pale and transparent looking.

I've seen studies looking at the interaction of other amphipods and Crangonyx sp. and it looks like Crangonyx are eaten by pretty much all the other Gammarus, Dikerogammarus etc sp., so I'm guessing you couldn't keep Hyalella and Crangonyx as a mixed culture, whereas I know that Asellus aquaticus and Crangonyx pseudogracilis can co-exist without any problems <"Predators vs. alien: differential biotic resistance to an invasive species by two resident predators">.

Whatever it is I have that I'm calling hyalella azteca is a pretty voracious predator in the abscence of any other food. They turn on each other immediately and definitely also eat asellus. I wouldn't introduce them to any tank that didn't have fish I was confident would eat them all or water that was too acidic and soft for them to reproduce well in.
I turned off my filter for feeding today and discovered that the baby crangonyx seem to have been hiding in my elatine hydropiper carpet. It does appear that they're a little more inclined to show themselves when there's no flow and this seems to confirm that at least some of them are escaping the dwarf kuhlis and axelrodi.

 

[dw1305]

Hi all,

on whatever fills a comparable ecological niche in brazil!

There definitely will be a crustacean in the "vegetarian shredder" niche, finding a name might be more difficult.

cheers Darrel

 

[bazz]

I wonder if H. azteca are just a lot "crunchier",

They defnitely look crunchier.

There's only one way to find out!

 

[dw1305]

Hi all,

There's only one way to find out!

Personally I'd be more than happy to do the "raw prawn crunch test", but unfortunately I only have Crangonyx, which would disqualify me. @louis_last has cultures of both species, so would be a much more qualified person for this ........

cheers Darrel

 

[louis_last]

Hey they steam cherry shrimp in bamboo and eat them in the east. I've definitely seen ray mears and bear grylls eat woodlice as a survival food. why not!
I've been giving my Dero worms the side eye ever since I discovered that they can be up to 70% protein. Imagine the gains. I'm thinking a chocolate flavoured Dero worm protein shake called "Vermighty" or something.