[Pavel Chaloupka]

[quote=”Vale!” post=3760]My own Moina culture method has been OK but results in a variable supply. Numbers will build until there are absolutely zillions of them, then recede until there are only a few hundred or so before building again! I’d like to achieve a more dependable supply [/quote]
Well, this is completely normal. We have to realize that this is how it works in nature with most of the populations of any creatures. Only what we see with Moina is extreme example of how it works, becouse Moina is transfering close to 70% of the total energy income in to the reproduction. What we can learn form this… As long as there is enough food and space and the envinronment factors are within the boundaries for the species( polution, temperature,oxygen, some light), the population will grow. With Moina this growing population typically consists of females only and these females are literally cloning themselves (you can try and start a population with a single female), so the more females there are, the faster the growth of the population. This is the stage of the population that we need to achieve to get enough food for the fish and we want to keep this going. Because we work with a closed system, at some point the population will reach the breaking point which means there is not enough of something( food, oxygen, space) or to much of something (waste products). Mostly it will be lack of oxygen and to much of waste product. Than almost all the organisms would die and the population will colapse. But even before that happens, we are getting to some unwanted field. Many organisms will stop the reproduction before their populations would colapse. Moina will only make changes to the process. Once the environmental conditions start to deteriorate, the parthenogenetic females give birth to sexual females and males. The sexual females start to produce ephippia (the resting eggs similarly as Artemia does). These will sink to the bottom and wait for better times to start the population again when conditions are good (in theory you should almost always be able to get some moina again if you let the bucket dry for one or two weeks and add some aged water) . Sexual females may switch back to the parthenogenetic reproduction any time, they only need one moulting for that but compared with a lot of Daphnia, parthenogenetic females of Moina can not switch to sexual reproduction, they need to be born as sexual females to have that ability.
So back to your question 🙂 My point with feeding the living algae to Moina si mainly much slower deterioration of the the environment becouse the unconsumed food does not polute the water and it is constantly available as high quality food. Also it is one of the natural foods so its very well digestible for Moina which again leads to less waste products and therefore less polution of the water. Also some algae and cyanobacteriae contain very valuable nutrients that work as probiotics, growth factors and color enhancers for the fish as well as source proteins and fats in the very form that is best for the fish. Thats for the algae.
What you need to do to keep the culture as we want it, so with parthenogenetic females only and constant reproduction, you need to harvest enough Moina and exchange enough water often enough (on daily basis if needed). This way you should be able to maintain the culture for quite a long time. Of course there is a catch. With partial water changes you only dilute the waste products to some extend. Imagine that you have 100% of polutants in the water and than you make a 50% water exchange with absolutely clean water. 50% of the previous polutants are still in the bucket and Moina will add to it again before you make another water exchange so the levels of the polutants are still growing, the whole process is just slowed down to some extend. Some day you will get to the point where these substances will reach sexual reproduction inducing levels or in the worst case kill the culture. Thats why we need to start the new cultures over and over. If you want continous and effective production, you need to built a drop system. You would start with algae cultivation medium that drops to the tank where algae are cultivated and then algae drop to the tank with Moina and Moina drops in the bucket or sieve where you gather it for feeding. This is how it is done in commercial hatcheries. I hope that helps. Sorry if I have to many spelling mistakes in the “article :D”, I am not patient enough to go trough it couple times.