Forum > Fish food, feeding and diet

Moina Miracle!

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Vale!:
Moina are creatures much like the more familiar Daphnia. There are both saltwater and freshwater species but I'm concerned only with the latter of which (I think) there are around six species.

They are slightly smaller than are Daphnia, and their similar movement triggers fishes'  hunting response ; however, depending upon what they've been fed, they are more nutritionally valuable.  Culturing is similar in most respects to Daphnia and so it should be feasible for the adventurous and suitably-equipped fishkeeper to have a bash! I have been maintaining Moina cultures, with varying degrees of success, for a few years but haven't been confident enough until now to recommend them to the Forum - either in terms of economics or of culture method.

The difficulty has been their availability in the UK. I have imported starter cultures from Carolina Biological, via their UK agent, Blades, but most may regard the shipping costs as somewhat prohibitive.  A little less so was an import from Germany.  I then spotted, on ebay, a seller in Malaysia who supplied ephippia (Moina eggs, if you will) at a very reasonable price.  I tried those and was relatively pleased with the results, although a myriad of other creatures hatched alongside the Moina!

I still knew of no reliable UK source until, four weeks ago, a speculative stab on ebay turned up this.  Here is the miracle referred-to in the thread title!

 I ordered one which arrived promptly. A bag contained around twenty individuals, accompanied by sachets of yeast and of Spirulina powder, an instruction leaflet and three Red Ramshorn snails.

I immediately cleared a small tank, by decanting its Moina residents into another culture, bleached everything apart from its air-driven filter sponge, reset the tank and followed the instructions (apart from the food, which I supplemented with extra ingredients).

I was able to harvest as from week two and I have already split the culture, but the first part of this video, taken a couple of days ago) gives an idea of progress.



I seem to be facing a Red Ramshorn apocalypse : they have been at it like knives. I have many dozen tiny hatched snails and at least a dozen egg-masses ready to produce more.  I can't think that there is enough food for them all to survive ; if they do I will have to think about introducing an Assassin snail or two.  The idea of co-culturing with snails is that they clean up much of the detritus that settles on the tank floor ; at the same time their poo generates infusoria and fungus which then form part of the Moina's diet. The second part of the four-minute video tries to give an impression of the sort of creatures that will populate the poo in much greater numbers than are present at the moment.  I have used just pond snails up to now. I may continue to use pond snails – comparatively speaking, they seem more able to contain their natural urges (unbelievable as that may seem)!

This latest culture has a thriving population of Ostracods - however that is not a surprise : they seem to be endemic at Vale! Towers and I suspect they emerged from the unbleached filter sponge when it was reintroduced to the tank. I try to remove a few along with each harvest of Moina, with a turkey baster.


Culture Notes

I have some in a tub in the garden but the following comments relate to indoor cultures.  I have no idea whatsoever why the closing italic tags are displaying below - though they seem to work OK! I also have no idea why my perfectly-formatted text (in preview mode) falls apart in places when posted [now fixed, I think, with a bit of engineering].


Redundancy[/I] : Any culture of this sort may be prone to collapse for no discernible reason! Hence it is best always to try to maintain at least two cultures to facilitate recovery.

Container[/I] : I've found that a glass, or acrylic, tank is best but a plastic tub or bucket could be used if it can be placed where its surface is well-lit.  A couple of 5-litre acrylic tanks that I made
            to fit on a windowsill did very well, the Moina it produced being noticeably bigger than their cousins kept away from sunlight. The largest tank I use at the moment is about 15 litres in volume. No
            substrate is necessary. A lid is advisable, if possible, to reduce evaporation - though if it's a choice between lid or light, the light wins!

Water/Temperature[/I] : I use reverse osmosis/deionised water, remineralised with JBL Aquadur to a conductivity of around 300uS/cm (I'm not precise at all about this!). Most UK tapwater, treated
            with a dechlorinator that reliably 'removes' heavy metals, should be eminently suitable - though I've not tried to use ours. Clean rainwater would be ideal.  I do small water-changes every so often.
            My cultures are at room temperature but would certainly benefit from being kept at around (say) 25C all year round - they are obviously more prolific in Summertime.

Filtration[/I] : I use air-driven sponge filters which provide gentle circulation (to help keep food in suspension) and better gas exchange at the surface.  An alternative is to have some plants in the
            container - I have used Pennywort but any plant touted as being an 'oxygen generator' would surely do. I don't think that a power filter (even a 'nano' one) would be at all suitable.  It's entirely
            possible to manage a culture without a filter at all, relying solely on water-changes to maintain water quality, though an airstone would be beneficial. If using an airstone, ensure that the bubbles
            are large ; small bubbles may become trapped under the animals' carapaces and cause them to be trapped at the surface.

Cohabitants/Decor[/I] : I mentioned the benefits of co-culturing with snails above.  I keep a piece of cuttlebone in each of my Moina cultures, mainly for the snails' benefit.

Water-Changes[/I] : this is a tricky problem because, it's well nigh impossible to syphon out water without also extracting significant numbers of rather baffled Moina! I've solved it by putting one
            end of my syphon pipe into a brine shrimp sieve and, holding both pipe and sieve with one hand, partially immersing that arrangement into the Moina tank. My other
            hand manipulates the pipe to my mouth and then to a suitable container. No Moina can get through the sieve, try as they might.

Food[/I] : Like Daphnia, Moina filter out tiny  food particles from the water.  The particles need to be a size of around 2-5 microns. This is easily achievable if you can culture 'green' water (which I
            do in a couple of jars on a windowsill) which will develop single-celled algae of just the right size and variety. It's possible just to use yeast to feed Moina but their eventual nutritive value to fish is
            reduced and they tend not to thrive as well as when they're fed a variety of food.  Anyway, I  use my green water as a base, put some in bottle (that I can keep in a mini-fridge) and add to it small
            amounts of one or two or three from the following list  (depending upon what I have available at the time) :

            Yeast. Just a small pinch of the dried form.

            Nannochloropsis* (a single-celled alga). Just a drop. I also add this to my green water culture.

            Chlorella** (another single-celled alga). Again, just a couple of drops ; and again, I use this in green water.

            Spirulina powder*. Just a tick on the very end of a teaspoon.

            Marine Snow. Contains particles found in seawater, but the product doesn't contain seawater! Marine Snow is made by Two Little Fishies but other brands of similar products are available from LFS's
                  or from online retailers. I add about 1ml to the mix in my little bottle.

            Dry Invert Feed*. A powder which, when hydrated, develops a variety of algae etc. that Moina (and Daphnia) love to eat. I use a large pinch of this.

            Rice 'Milk'.  When preparing rice for Mrs. V! I will occasionally wash it first in reverse osmosis water. The milky fluid that results is strained off and stored in the fridge. I add a couple of millilitres to
                 my bottle.

* I source these products from ZM Systems (other retailers may offer similar products).
** I get this from Sciento (ditto).


I'm sure that one of the chief causes of a culture's collapse is overfeeding. To help guard against my impressive proclivity in this regard, I make up small batches (about 100ml) in a squirty bottle and try to be as mean as I dare with it. When the bottle is half-used, I top it up with water again.

Harvesting is done with a turkey baster or, if I want a larger amount, a brine-shrimp sieve. 

I’ve checked with the ebay vendor that he is likely to be able to supply further kits (his stock is showing as “1 left” at the moment) and he said that he expected to be able to since he maintains four cultures.


Anybody else fancy giving this a go, then?!

Mol_PMB:
This looks intriguing, and I'm keen to give it a try :)
I should free up a 28L tank in the next week or two as I move my Dicrossus fry to a larger tank, so I might try that as a suitable vessel. I'd like to have more Ramshorns too!

plankton:
Well I think it needs to be a sticky......... ;) :)

Mol_PMB:
I've set mine up in a spare 10L tank, though it's only about 2/3 full at present. I've got an airline bubbling into it (no airstone) and it sits on a south-facing windowsill.

So far all seems to be going well and according to the instructions.

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