Controlling algae with daphnia

[Myrtle]

I had a random thought earlier, whilst pulling the duckweed from my jar-arium on the windowsill; I keep a colony of daphnia in there, along with a few shrimp and have from day 1. It's on a south facing windowsill, so gets a lot of sunlight, yet very little algae. There's a bit of hair/thread algae and occasionally (every month or so) I wipe the glass, but that's it. It gets a squirt of ferts when I remember and is topped up with either aquarium water or rainwater, whatever is to hand. I wondered if the daphnia are helping to control the algae by filtering out the spores? If so, could we use this to our advantage while a tank establishes? It may have been discussed before, but I couldn't find anything...

 

[MichaelJ]

daphnia are helping to control the algae by filtering out the spores?

I think they would help doing that.

If so, could we use this to our advantage while a tank establishes? It may have been discussed before, but I couldn't find anything...

I like where you're going with this... sounds like a brilliant idea. I would definitely like to hear others thought on this as well.

Setup tank, add plants, a week or so later add daphnia! … way before livestock. Darn it, I wish I could run an experiment like that.

Cheers,
Michael

 

[hypnogogia]

And fresh food for when the fish are introduced…

 

[SteveMid]

It’s very interesting that you ask this because I think I may have observed exactly what you are suggesting. I have a vat outside with old rain water in that I leave alone and occasionally harvest mosquito larvae for my tropical tank. At the end of April the water was a horrible green/brown and I could not see the bottom. I threw in about 10/20 water daphnia that I had left over as I was going away. When I returned a couple of weeks later the water had started to clear and there had been a population explosion of water daphnia (first picture). I harvested a few to feed my fish tank but left a large population still in. Three weeks later (second photo) the water is gin clear.😀

 

[Tim Harrison]

it’s not such a bad idea. Phytoplankton and zooplankton are the basis of intricate aquatic food webs. And daphnia is a keystone zooplankton species. However, the spanner in the works might be a canister filter hovering them all up, for instance.

 

[_Maq_]

All reports known to me (plus my little experience) seem to confirm that Daphnia hates flowing water.

 

[Myrtle]

Ah, I forget the flow in high tech tanks! Maybe for low tech tanks?

 

[zozo]

All reports known to me (plus my little experience) seem to confirm that Daphnia hates flowing water.

That's indeed a major point of concern Daphnia requires an about stagnant environment and a turnover from an external filter is deadly to them and it won't take long for them to be all gone into the filter or stuck to the mesh of the inlet. I also tried it a few times to use them at tank startup as first inhabitants but failed of course due to filter turnover.

What could work is using an old fashion internal airlift sponge or cotton filter with very little turnover. And no airstone but one that creates big air bubbles.

The old fashion one.

A fine air mist in the water is equally deadly to them it will trap them covered in airmist no longer able to swim.. Or use one with an outlet above the water line. But the turnover should still be very gentle.

The more modern designs.