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parasites on scuds and Daphnia crashes
Reply to Daphnia crash:
Excessive food (e. g. moldy cucumber) can crash a Daphnia culture. A single culture should be backed up with several others. If you have several, when one inevitably crashes, you can sterilize the container and split a strong culture. Sometimes Daphnia will reappear from resting eggs in a crashed culture if it is allowed to sit without fish for a few weeks and if the water is kept hard and alkaline. Daphnia usually come from still water, so excessive circulation is a stress factor that could encourage a crash. Yeast and crushed flake foods are not the best diet for Daphnia. There are a variety of foods from green water to Brineshrimpdirect.com's Tahiti algal paste, to to Marc Weiss' Spectra Vital and Blackpowder to homemade foods (recipes in archives) that are much better than yeast and flake food. When a culture is growing rapidly, it's paramount to harvest so that the population remains steady. There will be a certain hard-to-define population that is more than the culture can sustain and that will be the end of the culture. Daily removal of 20% of the water and Daphnia from the strong culture and replacement with green water or buffered, aged fresh water can keep the culture going indefinitely. That is also the time to split cultures. New cultures can be started by collecting the largest Daphnia with the coarsest screen or net that will catch any Daphnia at all. In some strains, males are smaller and males are unwanted because they end the live birth of daphnia and cause a cycle of resting eggs to at least temporarily end the productive life of the culture.
Parasitic worms associated with freshwater scuds:
Look on the bodies of the scuds for small red dots. If you see any of these, the worm you saw may be a parasite and in any case only the forerunner of many more. If these parasitic worms become established in the aquarium, they will be difficult to eradicate. Many small aquatic worms are not parasitic, but any worm associated with any species of amphipod should be suspect.
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