Daphnia & Cyclops

[Humanist]

Having noticed that when washing shop bought daphnia in a net some of the very small ones slip through the mesh, I decided to keep them and attempt to grow them to a reasonable size to feed my fish. The two options for me were to put them in tank water, or into green water collected from a discarded bucket in my garden. I decided to try both options.

I cut the top off two 2L lemonade bottles, rinsed them out and part filled one with tank water and one with green water and then added the tiny daphnia.

After a few days, both bottles seemingly had more daphnia than I started with, with the green water bottle in the lead as far as growth went.

A few days later though, the numbers in the green water bottle appeared to be falling. Then I noticed that the daphnia in the green water looked a bit different, and moved faster through the water than the tank water daphnia. I collected a sample from each bottle and examined them with a 10x magnification illuminated jewellers loupe.

It turns out the creatures in the green water bottle are actually cyclops - not daphnia. There are absolutely no daphnia left in that bottle. I have no idea if the daphnia were killed or eaten by the cyclops, or if they died due to unsuitable water chemistry in the green water bottle, or something else. The cyclops are thriving in the green water, many of them carrying twin egg sacks which are clearly visible through the magnifier.

So I have a colony of daphnia and a colony of cyclops in seperate bottles. There are no cyclops in the daphnia bottle, so presumably the cyclops came in with the green water from my garden.

The question is, are the cyclops safe to use as fish food?

 

[Baccus]

I am pretty surew that cyclops are ok as fish food, but some fish can find them a bit though shelled. Also I am led to believe that adult cyclops are not safe with fish fry, therefore if feeding cyclops to your fish only feed enough that they are all eaten and don't get a chance to mature and go on breeding in your tanks.

 

[BigC]

So long as you use them as food for larger fish and not fry. They will attack fry, which probably explains whats happened to your Daphnia culture. They probably will have attacked the young Daph. although I would find this a little hard to believe as Daph reproduce (if conditions are right) at an alarming rate. Have a look for dark (black) egg casings...these will look like very small seeds. If you can see these, they are ephippia. Daphnia employ a canny way of ensuring their survival. Do a little more research on their reproductive cycle (Parthenogenesis) this will explain how and why you are seeing these tiny sacs. basically if conditions are infavourable (water, temps, food, predators) then the daph will produce, what is in effect resting eggs.
If you are looking to experiment again using algae from a virgin source please read my article in the killifish section
http/www.fishforums.net/index.php?/topic/340027-forty-shades-of-green/
There are also other articles of my work with Daphnia pulex, Moina macrocopa and various shrimp...all employing algae as food.
I hope that helps you somewhat.
Regards
BigC

 

[Fishrule]

I've seen cyclops sold in my lfs, but only for bigger fish