Copepods during the day but not at night?

[Bbio]

I have pods like this completely covering my whole tank when I get home from work every day. They’re extremely small but they’re crawling all over the glass.

But at night, if I go at the tank with a flashlight, I hardly see any on the glass. And they’re too small, no way I’d be able to see them on the rock work.

Are they copepods or something else? Everything i see says the population should be more visible during the night, not during the day.

Tank is almost 10 months old 150 gallon with a chaeto fuge. I just got a mated pair of Dragonets and now I’m stressing worrying if they have enough food so I dosed more pods.

 

[Mr. Mojo Rising]

Pods on the glass is not a good measurement of the amount of pods in the tank IMO. The majority of them are in the rocks and sand. If you see your mandy hunting non stop, eating a pod every few seconds, then there are plenty of pods. If you see mandy sitting on the sand for long periods of time, there are not enough pods.

 

[keagan]

I wouldn't rule out copepods because of diurnal behavior. Not all copepods are strictly nocturnal. Some species can be active during the day like harpacticoids that graze on biofilms. In aquaria, behavior is also influenced by predator pressure and food availability, so seeing them on the glass during the day and retreating into the substrate at night is plausible. It's funny how it's basically a reverse of how diel vertical migration is normally observed (not in a scientific sense in an appearance sense)

 

[EnterName]

I would frequently add pods while keeping dragonets regardless of the perceived population. There is no reliable way for me to measure the pod density on the rocks and I observed that dragonets often stick to the rockscape and don't go for the pods sitting on the glass.

That being said, you should notice when your fish starts looking thinner and thinner.

To actually identify what you got on the glass you would need a decent magnifying glass/macro lens or even better a microscope. The chance of it being something else than pods is low though.

I could imagine they are grazing on a biofilm that grows large while light is available and then switch to the rocks and substrate when it gets dark and the biofilm no longer grows. Certain dinoflagellates for example would match this criterion but there are certainly photosynthetic bacteria as well that would behave this way and cause pods to switch their preferred spot throughout the light cycle.

This is obviously just a hypothesis we would have to verify first.

 

[Bbio]

I would frequently add pods while keeping dragonets regardless of the perceived population. There is no reliable way for me to measure the pod density on the rocks and I observed that dragonets often stick to the rockscape and don't go for the pods sitting on the glass.

That being said, you should notice when your fish starts looking thinner and thinner.

To actually identify what you got on the glass you would need a decent magnifying glass/macro lens or even better a microscope. The chance of it being something else than pods is low though.

I could imagine they are grazing on a biofilm that grows large while light is available and then switch to the rocks and substrate when it gets dark and the biofilm no longer grows. Certain dinoflagellates for example would match this criterion but there are certainly photosynthetic bacteria as well that would behave this way and cause pods to switch their preferred spot throughout the light cycle.

This is obviously just a hypothesis we would have to verify first.

I’ve had them for about a week. They weren’t terribly skinny when I got them from my LFS, they still aren’t, but they’re not fat. I added a culture of pods with them but won’t be able to add more for another week and a half.

How often should I be adding pods?

 

[EnterName]

I would frequently add pods while keeping dragonets regardless of the perceived population. There is no reliable way for me to measure the pod density on the rocks and I observed that dragonets often stick to the rockscape and don't go for the pods sitting on the glass.

That being said, you should notice when your fish starts looking thinner and thinner.

To actually identify what you got on the glass you would need a decent magnifying glass/macro lens or even better a microscope. The chance of it being something else than pods is low though.

I could imagine they are grazing on a biofilm that grows large while light is available and then switch to the rocks and substrate when it gets dark and the biofilm no longer grows. Certain dinoflagellates for example would match this criterion but there are certainly photosynthetic bacteria as well that would behave this way and cause pods to switch their preferred spot throughout the light cycle.

This is obviously just a hypothesis we would have to verify first.

I’ve had them for about a week. They weren’t terribly skinny when I got them from my LFS, they still aren’t, but they’re not fat. I added a culture of pods with them but won’t be able to add more for another week and a half.

How often should I be adding pods?

Could be a bit skinny but this is unfortunately a very common sight when buying dragonets from an LFS. Not your fault.

I think you will need to develop a gut feeling on how frequently you have to stock up pods to be safe. It will heavily depend on the tank size and how much food is available to the pods. If the whole glass is full I could imagine you have time and don't need to add pods for the moment

Just see if the dragonets are getting thinner or fatter and then maybe add some pods every other month or so depending on the development you observe. It's more a safety net than anything else if the tank is well established.

 

[Bbio]

I would frequently add pods while keeping dragonets regardless of the perceived population. There is no reliable way for me to measure the pod density on the rocks and I observed that dragonets often stick to the rockscape and don't go for the pods sitting on the glass.

That being said, you should notice when your fish starts looking thinner and thinner.

To actually identify what you got on the glass you would need a decent magnifying glass/macro lens or even better a microscope. The chance of it being something else than pods is low though.

I could imagine they are grazing on a biofilm that grows large while light is available and then switch to the rocks and substrate when it gets dark and the biofilm no longer grows. Certain dinoflagellates for example would match this criterion but there are certainly photosynthetic bacteria as well that would behave this way and cause pods to switch their preferred spot throughout the light cycle.

This is obviously just a hypothesis we would have to verify first.

I’ve had them for about a week. They weren’t terribly skinny when I got them from my LFS, they still aren’t, but they’re not fat. I added a culture of pods with them but won’t be able to add more for another week and a half.

How often should I be adding pods?

Could be a bit skinny but this is unfortunately a very common sight when buying dragonets from an LFS. Not your fault.

I think you will need to develop a gut feeling on how frequently you have to stock up pods to be safe. It will heavily depend on the tank size and how much food is available to the pods. If the whole glass is full I could imagine you have time and don't need to add pods for the moment

Just see if the dragonets are getting thinner or fatter and then maybe add some pods every other month or so depending on the development you observe. It's more a safety net than anything else if the tank is well established.

Alright. I appreciate your advice. I was worried about the next week and a half.

It’s a 150 gallon tank with a refugium in the 40 gallon sump.

The mandarin pair are the only pod eaters besides a clown and pair of yellow tail damsels. But I’ve never observed any of those 3 picking at the rocks, only eating prepared foods.

 

[Bbio]

 

[EnterName]

I would frequently add pods while keeping dragonets regardless of the perceived population. There is no reliable way for me to measure the pod density on the rocks and I observed that dragonets often stick to the rockscape and don't go for the pods sitting on the glass.

That being said, you should notice when your fish starts looking thinner and thinner.

To actually identify what you got on the glass you would need a decent magnifying glass/macro lens or even better a microscope. The chance of it being something else than pods is low though.

I could imagine they are grazing on a biofilm that grows large while light is available and then switch to the rocks and substrate when it gets dark and the biofilm no longer grows. Certain dinoflagellates for example would match this criterion but there are certainly photosynthetic bacteria as well that would behave this way and cause pods to switch their preferred spot throughout the light cycle.

This is obviously just a hypothesis we would have to verify first.

I’ve had them for about a week. They weren’t terribly skinny when I got them from my LFS, they still aren’t, but they’re not fat. I added a culture of pods with them but won’t be able to add more for another week and a half.

How often should I be adding pods?

Could be a bit skinny but this is unfortunately a very common sight when buying dragonets from an LFS. Not your fault.

I think you will need to develop a gut feeling on how frequently you have to stock up pods to be safe. It will heavily depend on the tank size and how much food is available to the pods. If the whole glass is full I could imagine you have time and don't need to add pods for the moment

Just see if the dragonets are getting thinner or fatter and then maybe add some pods every other month or so depending on the development you observe. It's more a safety net than anything else if the tank is well established.

Alright. I appreciate your advice. I was worried about the next week and a half.

It’s a 150 gallon tank with a refugium in the 40 gallon sump.

The mandarin pair are the only pod eaters besides a clown and pair of yellow tail damsels. But I’ve never observed any of those 3 picking at the rocks, only eating prepared foods.

I don't think the next two weeks should be an issue. Dragonets eat a lot of pods but they reproduce fast and you just added some. 10 months is quite young, but if the pod population appears dense it's likely fine as long as you maintain it that way. I could imagine the glass being a decent indicator of the overall population even though that is hard to prove and the reason why I would rather add too many than too few.

As long as the dragonets keep gaining weight it should be fine. Maybe you get lucky and they start eating some frozen food, too.