Daphnia Culture growing out from eggs.

Daphnia Culture Eggs
1 – Buy Resting Eggs

This is pretty basic stuff and IF you do everything I suggest below, I personally guarantee success.

Select a clean container of at least 10liters (~2.7gallons) made from food grade plastic, glass, perspex or 316 marine grade stainless steel fish tank.
All of these I recommend.
I personally use 10-55litre plastic tubs or roller boxes.
Cheap, comes with a lid, and is the ideal size.

You may later have success using old 44gallon drums, bath tubs, cattle troughs, even soft drink bottles, ice cream containers and yogurt tubs, but due to the variables in material, chemical, mineral and metal leakage risks, I can not recommend them in this initial delicate establishment stage.

Establish the culture first, keep it happy and healthy for a couple months, then later as numbers build you can split it and do experiments using other containers.
All the while keeping a back-up safe and happy, just in case.

2 Add resting eggs to rainwater and aerate.

Add Daphnia Eggs to Rainwater
2 – Add Eggs to Rainwater

Add Rainwater and eggs to your chosen culture vessel.
You can apply the easy peel sticker to the culture vessel too, so you don’t loose track of which species you are growing. Makes it much easier to tell your friends where you got them from too…

An airline without an air stone will increase hatch % and speed things up quite a bit. Stir vigorously every 3 days really scrubbing the tank walls and stirring the sediment around. This is VITAL for high hatch rates and you must continue to do this.

A clean piece of wood or long bamboo chopstick is ideal. This allows algae and sediment to be within reach of the tiny larvae, and it prevents the water fouling. It also allows the sediment to be mixed around letting every egg in the packet to get wet and makes sure no critters get trapped underneath. Do this in a rough swirling motion so any floating eggs get washed away from the sides of the tank and into middle where they sink. This stops them getting trapped high and dry.

3 Patiently wait two weeks to a month.

Patiently wait 2 weeks to a month
3 – Patiently wait 2weeks to a month

In good conditions about 2-4weeks later the critters will begin to hatch. If you live in an area with cold night time temperatures then using an aquarium heater set at 15-30celcius (60-85farenheit) will increase your hatch rate and speed things up.
Lower or higher temperatures, even for a couple hours, in just one day out of the whole month may prevent hatching altogether. Keep this in mind.

Once you see several hundred creatures you can begin feeding them. They will eat algae, flour, or even just mashed frozen vegies, but the very best foods for them are kept here. Daphnia Moina food.

4 Remember to stir

Stir every three days
4 – Stir every three days

Keep stirring the water and sediment every three days so the water stays nice and clear. This mixture of sediment and algae that you stir up is their main food and it important that they can get at it in the water column. They have a lot of pride and don’t like to pick up their food off the ground!

Do not overfeed!
Cloudy water = too much food = DEATH!!!

Remember that although there may be hundreds or even thousands of creatures visible, they eat algae and bacteria all day long, and this food is already produced naturally in their tank. It is too small to see, so just trust me on this.

5 Successful hatching of eggs!

Hatching Daphnia eggs
5 – Hatching Daphnia eggs!

If the water is cloudy I do not feed at all. Very hard to do, but “tough love” is better than “killed with kindness”. They have not eaten their dinner, so they don’t get desert until they do!

You do not have to add food at all if you only want them as pets. No added food added to the ecosystem means numbers will stay small, and your tank will stay much cleaner.

If your plan is to harvest for fish food, or you just want a lot of pets then feeding, aeration and large tanks will produce large numbers that can handle regular harvesting.

How do I get really high densities?
Aeration WITHOUT air stones in large containers. Air stones make super small bubbles that get stuck under the shells of mature adults. This makes them float on the surface where they can not feed and eventually die. Air stones are also made from rocky sandy minerals that are glued together and shaped around a connection. This glue and metallic mineral mixture is normally 100% harmless to fish, BUT, it is often very toxic to Cladocera and other mini-critters.
DO NOT use air stones. If you do, you will nearly always have more “crashes” where they all die unexpectedly, or the reproduction rate will be lower in general.

I use the slightly more expensive 316 marine grade 1/4inch stainless steel Hex nuts. Do not use normal steel or zinc coated nuts, as that will often kill them via metal leaching. They fit standard 4mm air hose snuggly, not interfering with the airflow or falling off. The SAE 316 stainless steel does not rust, corrode or give off nasty chemicals, and it has no effect on growth rates in my trials. In all honesty, after trialing heaps of different things, these are bloody PERFECT!

Cosy warm temperatures. If you live in an area with cold night time temperatures then using an aquarium heater set at 15-30celcius(60-85farenheit) will increase your reproduction rates and densities. ~20% water changes using clean aged rainwater every week or so can really help if your plan is continual culture of high densities, or as food for fish.

Calcium.
These guys are crustaceans, meaning they have a chitinous or calcareous exoskeleton. Like a crab, yabbie or lobster. This takes a lot of calcium to produce and if you want lots of healthy critters, then dried shells and sandy grit is a great way to provide it gradually.

I sell small bags of my Shellgrit Substrate Mix here, and although not necessarily, it really does improve general success rates and provide much higher densities, or critters per liter of water. It also aids the buffering of pH slowing or stopping altogether the swings that algae and bacterial blooms bring. Even better still, it provides a very porous surface and is the ideal media for beneficial bacteria to grow on, in turn improving water quality and clarity.

TLDR
Use a food safe container, add rainwater and eggs, keep warm and stir every 3days.
=Success!

Use larger containers, add more air and calcium.
= MEGA SUCCESS!!!

Anything else
= an experiment I have no experience with.
Could be good, could be bad, no idea, so I can’t recommend it.