Daphnia Breeding Question

[fishmom]

I am trying to breed daphnia and have a culture going. My question is...I keep getting a collection of mulm/junk type stuff at the bottom. Am I doing something wrong to make that happen? They have an airstone and some slow growing floating plants. How do I clean it out without throwing out a bunch of babies? 

[Fish Folk]

Daphnia generally require a normally cycled tank like aquarium fish. If you do not have a filter going, it is possible that what you're seeing is just bacterial buildup. Daphnia feed on bacteria as well, so perhaps this is just the accretion that is building up. Add a small sponge filter. They should multiply for you if all is well in their environment. They do appreciate a normal schedule of water changes. Having said that . . . every Daphnia keeper I know has plainly told me, "Keep two colonies going! They do crash easily." I've tried them several times with limited success. Outdoor mini ponds seem to be the best environment to see them thrive. 

[Patrick_G]

I recently bought a small starter colony and I'm reading lots of conflicting advice. I’m glad this topic came up. Should I be trying to keep these in a small tank with a heater and a nano filter? Should I be feeding them anything besides yeast?

[modified lung]

On 11/30/2022 at 4:48 PM, Patrick_G said:

I recently bought a small starter colony and I'm reading lots of conflicting advice. I’m glad this topic came up. Should I be trying to keep these in a small tank with a heater and a nano filter? Should I be feeding them anything besides yeast?

No heater necessary. Definitely keep them below 80°F or they'll slow reproduction. I've never used a filter with them. I like greenwater and spirulina powder but yeast works too. Give only very small amounts of any dry feed. They eat more in low light so crashes are less likely if fed in low light. The smaller the tank the easier they crash regardless of water quality. 5 gallons works fine.

The best Daphnia culture I ever had was in a shallow outdoor tank of rain water with cow manure. It grew very dense and stayed that way for over 3 months with no intervention besides harvesting. 

[TOtrees]

I think daphnias are quite tolerant of imperfect water. In nature, they often thrive in ponds that dry up completely by mid summer, and in the days weeks prior to that occurring, the density of daphnia in the water can be nearly soup-like. 

I’m with @modified lung regarding feeding. I feed spirulina powder (I mix it with chick pea flour and rice flour at around 4:1:1 sp:cpf:rf), because I rarely have access to green water. I feed about a heaping 1/4 tsp daily, mixed in water before adding. I do vary the rate of feeding based on water clarity and population in each culture. 

My cultures are in a 20h and a 5 gallon bucket. In the 3? years I’ve kept them, I’ve had only a couple crashes, and (thankfully) never both at the same time. 

With all that food going in daily, I get a fair accumulation of mulm at the bottom, as with any tank it’s a combination of food that sank before eating, and biological waste/poop (yes, daphnias do it too). I MAYBE vac that sh1t up once every 6 weeks or so. My cultures have lots of snails to recycle it, which helps. And yes I have to thin the snail population once in a while. 

I combine water changes with harvesting. When I want to feed Daphnia to my fish, I use a python to remove say 5 gallons from the 20 gallon tank. I replace that with tank water from another tank. I have read that dechlorinators are bad for Daphnia, so I use anything but tapwater. I simply filter the removed water (with the daphnias in it) through a reusable metal coffee filter, then feed them to the tanks. 

Edited December 1, 2022 by TOtrees

[modified lung]

On 11/30/2022 at 11:27 PM, TOtrees said:

I have read that dechlorinators are bad for Daphnia

Can confirm.

On 11/30/2022 at 11:27 PM, TOtrees said:

(I mix it with chick pea flour and rice flour at around 4:1:1 sp:cpf:rf)

I might try something like this. I've been noticing the more you give a varied diet to other water fleas, they better they do.