..................................................Raising Moina macrocarpa Outdoors........................................................
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Moina are small freshwater crustaceans closely related to daphnia. Being smaller than daphnia, they are particularly valuable as a food for killie fry as well as smaller adult killies. Furthermore, they have several additional qualities over daphnia (easier to raise / more prolific / adaptable to higher water temperatures / able to reproduce well even in low oxygen level more polluted water / etc.) Newly hatched moina are in the range of 350um to 400um making them smaller than newly hatched brine shrimp (450um). This makes them an appropriate first food for smaller killie fry that can not be started on baby brine shrimp. In addition, the environment (water) that maintains a thriving moina culture will also contain significant quantities of rotifers, infusoria, and other phytoplankton making it a complete first food for any tiny killie fry. Adult moina top out at 800um to 1000um and are about half the size of daphnia.
I will detail the procedure I use to raise large quantities of moina outdoors.......this procedure should work for any / all killie hobbyists with a minimum of effort / expense.....I start out with three (3) used 55gal plastic drums....they are approx. 34.5 inches high and 23 inches in diameter. I've seen them in multiple colors (white / blue / black / etc)....White is much preferred for reasons I will detail later. They are routinely available on e-bay from multiple sources. I am particularly fortunate to be within driving distance of a source in New Jersey which offers used BPA Free drums at 3 for $27 with easy local pickup. A sabre saw is used to cut the top out of the drums for easy access. These drums (1 white and 2 blue) were set up on the west facing wall of my home. This was largely due to the fact that it was on the rear wall near the garage entrance with a water faucet nearby. This location gets no sun until mid afternoon and then only a few hours before it again becomes shaded by a large red maple tree. Ideally in a wet year, rainwater will keep the barrels full all summer. In a dry summer, water will need to be added as needed to keep the barrels full. Initially, I used chlorinated city water from the tap treated with Seachem Prime. It is hard (about 240PPM) and around 7.6 pH. Top up water is untreated city water since 10% at most is required. I do not use aeration (for convenience) although mild aeration has been shown to increase production.
For convenience, I feed exclusively with yeast (Red Star baking yeast in 2 lb bag available on Amazon for $16) although many other foods can be used. It lasts me over a year. My feeding procedure involves the following. I have a 1.5 liter graduated plastic capped bottle to which I add 1 tablespoon of yeast. I then fill with lukewarm water and shake vigorously to suspend all the yeast. I try to feed every other day but a strict schedule is not required. I harvest the moina with a fine net first and then distribute 500ml of the yeast/water mix into each drum.....That's it. It took me awhile to notice the white drum always produced more than the other two blue drums especially when I only sporadically fed........It took me longer to figure out why. The water in the white drum always appeared off color somewhat in comparison to the somewhat clearer water in the blue drums. I believe the additional amount of light transmitted thru the sides allowed for a more robust phytoplankton population which led directly to a more robust moina population. This was particularly noticeable and reproducible in times of little to no artificial feeding. If I kept up a semi routine feeding schedule, I saw little to no difference in production barrel to barrel. One thing is certain. If the water in the drum turns near perfectly clear with high visibility thru it, you are not feeding often enough or in sufficient quantities. If this persists for too long, the moina production will go way down or crash totally. Normally, a population in high growth mode will be all females with asexual production. However, in times of stress, some males are produced leading to sexual production and resting eggs. This should be avoided during the summer but is unavoidable in late fall when the temperature of the water drops into the 40s. Some of these resting eggs GUARANTEE that the moina come back every spring with no further introductions. The drums do no freeze solid in the winter and have not cracked in the many years I've maintained them. I can't honestly say why. But, they start to thaw by mid March and by early April, the huge floating plug of ice is all gone. Within a couple weeks, the moina faithfully reappear.
Moina are EXTREMELY productive. Females can reproduce after one week or less and average perhaps 13 in each brood with broods two days apart and an average 4 broods in their lifetime. While daphnia populations are subject to crashing at high population densities, moina are not. It has been demonstrated that moina can sustain densities ten times that of daphnia. In one experiment, under ideal conditions of feeding phytoplankton cultured on organic fertilizer, moina production was reported to exceed 5 ounces/100 gallons (375 g/m3) daily. REMARKABLE. Just as important is the fact that moina continue to produce strongly all summer at water temperatures up to 88F and at very low dissolved oxygen levels.. They also take huge daily temperature variations in stride. Tough little buggers!
I strongly suggest for anyone who is considering trying this to read the University of Florida reference article below. It includes everything you need or want to know about moina production. It even details freezing or freeze drying for long term storage. What I have detailed is the minimum effort required to have a continuous supply of moina available from late April to late October in my area (upstate NY)....I currently feed moina to 15 aquariums at least three times a week. I estimate I could harvest a solid ounce of moina every other day from the three drums (165 gal) when a regular feeding schedule is maintained. I'm sure production could be substantially increased with more effort and by following some of the suggestions in the University of Florida publication. But, I doubt more could be produced with less effort, which at this stage in my life is paramount. I'm going to add a drum or two indoors this winter to see how easy it might be to raise them indoors....Even 110 gal of water is much more than the average killie guy could/would devote to live food. I envision no stopper of shows and can easily add LED lighting if necessary. I also plan to investigate whether one can segregate by size the various little critters in the moina barrel. To that effect, I have obtained an array of sieves (40/60/80/120/200 mesh) corresponding roughly to (400/ 250/177/125/74 microns) costing $31 total. But since my eyes simply ain't what they used to be, a cheap microscope likely is in order So, by this time next spring, I might have another good story to tell. As they say....stay tuned. In the meantime, consider raising moina. You will not regret it.
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