Daphnia magna starter cultures

I think I’m getting the hang of this…

I hope I don’t jinks things by saying this, but my Daphnia cultures have never been better!

I almost lost my Daphnia this summer do to heat and the crashing of my green water culture, but they have made a marvelous recovery and are producing better than ever.

Here’s a short video of a daily Daphnia harvest.

With two 40 gallon breeder tanks going with green water cultures, and feeding a modified version of Doug Sweet’s dry Daphnia feed, I’m now producing enough Daphnia daily to supply all of my breeders and still have some left over.

Past Failures

When I started out culturing daphnia, my biggest stumbling block was failure to harvest enough. I would start with a small starter culture and nurture it along watching it grow day-by-day. I kept thinking, “I’ll give it one more day before harvesting”, and many times that one more day turned out to be one day too long.

Another problem I had was not feeding the culture properly. This is probably the toughest hurdle to overcome on the way to a successful culture. Feed too much and your culture will crash. Feed too little and your culture never thrives. Having a larger supply of green water will help, as you can’t really over-feed when feeding green water. The down-side being, you need lots of green water. A single ten gallon culture of daphnia can easily go through 3 gallons of green water daily.

My Keys to Success

There is a lot of information on the Internet about culturing Daphnia. Most of it is really good stuff, but I found that much of it either didn’t work for me, or was impractical for my needs.

My goal with culturing Daphnia is to have enough each day to feed roughly 100 fish to aid in getting them into breeding condition. I also would like to have enough excess to make up some starter cultures for on-line sale and at the local swaps & auctions. With those goals in mind, here are what I believe to be the most important

  1. Keep more than one culture going at all times. If you have a back-up, it does a couple of things for you. First, if something goes haywire, you have enough Daphnia to start up another culture. Second, just having a fall-back position, takes some of the pressure off of you when working with your main culture. Always have more than one culture!
  2. Have a schedule for harvesting and follow it religiously. I harvest a culture every third day. That works out to Day 1 feed – Day 2 feed – Day 3 harvest & water change. That works very well for me as I feed a dry mix with green water. Rather than net the Daphnia when I harvest, I drain water through a sieve. The water drained out is discarded and the harvest procedure works as a water change too! Always follow a harvest schedule.
  3. Get comfortable with feeding and what you feed. If I could, I’d feed almost 100% green water. It has many advantages with the biggest being you can’t over-feed and ruin your water quality. Maybe some day I’ll achieve that goal, but in the meantime, I have a dry mix of bakers yeast, pea flour, and a couple of algae powders that I feed along with the green water. Unfortunately there is no cut and dried formula for feeding your culture. It’s mainly something you just get a feel for with enough experience.

Future Plans

Always looking ahead, I’d like to get my Moina cultures doing as well as my daphnia. I wasn’t quite a lucky with my Moina this summer and completely lost my cultures. Fortunately, my friend Bill Trevarrow at Eugene Research Aquatics was kind enough to send me some starter cultures to get me going again.

Moina is of a smaller size than Daphnia, with a higher protein content and is perfect for fish too small to eat Daphnia, and also for growing out fry. I am especially fond of culturing Moina in grow out tanks of fry where the fry eat both the green water and the newly hatched Moina. Newly hatched Moina are roughly the same size as baby brine shrimp.

I’m also hoping to put together some cultures and a dry food mix for Daphnia & Moina that I can sell to other hobbyists. The many benefits of feeding live foods to fish you are trying to spawn just can’t be emphasized enough.