水蚤喂养十分简单，现介绍喂养的方法如下：
拿 到水蚤的虫种后，把袋子打开通气。准备一个十加仑（大约40升水）的大容器来养殖水蚤。养殖水蚤的水质极其重要，对待水要象对待你的鱼一样，千万不能让水 里有金属和有毒物质。准备好已注入水的大容器后，把装水蚤的袋子放在水中，让它在水面上漂20分钟。养殖水蚤的容器每天需16个小时的充分光照和良好通 风，理想温度为21～27摄氏度。
喂养水蚤：把相同份量的马铃薯薄片，鱼食薄片和酵母碾成粉末。取四分之一茶匙（10加仑的养殖缸所需份量）的粉末溶入适量水中，然后把水倒入水蚤养殖缸。在水变得象水晶一样清澈之前，无需再往养殖缸中添加饲料。
也可以用酵母来喂养水蚤，普通的面包酵母就可以了。把酵母溶入适量的水中（注意加入适量的酵母，否则会导致水蚤缺氧），把溶化了酵母的水倒入水蚤养殖缸。水变得有些黑，在水恢复水晶般清澈之前，无需再往养殖缸中添加饲料。
每星期更换一至两次水，每次更换水蚤养殖缸里25％的水。确保添加的水里不含氯，并和养殖缸里的水有相同的温度。
以上内容和建议，仅供参考。
水蚤在缺氧时呈红色，富氧时是透明的颜色
水蚤的血液含血红素，血红素溶于血浆，肌肉、卵巢和肠壁等细胞中也含血红素。血红素的含量常 随环境中溶解氧量的高低而变化。水体中含氧量低，水蚤的血红素含量高；水体含氧量高，水蚤的血红素含量低。由于在污染水体中溶解氧含量低，清水中氧的含量 高，所以，在污染水体中的水蚤颜色比在清水中的红一些，这就时水蚤常呈不同颜色的原因，是适应环境的表现。我们可以利用水蚤的这个特点，判断水体的清洁程 度。水蚤是指水生枝角类和挠足类两大类浮游动物，其营养丰富、容易消化，是鱼苗、鱼种的适口饵料。人工培育水蚤喂鱼成本低、鱼类生长快、增产效果好。其方法是：
一、建池 土池和水泥池均可。池深约1米，大小以10平方米～30平方米的长方形为宜。
二、注水 池中注水约50厘米深。水蚤适宜的水温为18℃～25℃，pH值为7.5～8，溶氧饱和度为70％～120％。
三、施肥 土池每立方米水体投4公斤牛、马粪或其他畜粪、1.5公斤稻草、麦秸或其他无毒植物茎叶作基肥，10天后追肥一次，追肥量同基肥，此后再根据水色酌情追 肥，使水色保持黄褐色。水泥池每立方米水体投牛、马粪或其他畜粪1.5公斤，加沃土1.5公斤～2公斤，以后每隔8天再追肥一次，追肥量为牛、马粪或其他 畜粪0.75公斤。
四、培育 不论是土池还是泥池，都可采用酵母与无机肥混合培养法。每立方米水体投酵母20克，酵母可先在水中浸泡3小时～4小时，再泼入池中，每立方米水体施碳酸铵 65克、硝酸铵37.5克，以后每隔5天施一次，其用量为开始的一半。投放酵母后，将池水曝晒1天～3天后，就可以放入水蚤作种，用种量为每立方米水体 30克～50克。
五、捞取 水蚤种入池15天～20天后，经大量繁殖，可布满全池。这时，即可分批捞取喂鱼。一般每隔1天～2天捞取一次，一次捞取总量的10％～20％。在水温18℃～20℃的环境下，可常捞常有，连续不断。
首先，准备一个容器，小缸子、宠物盒、保特瓶等等，都可以，最好的建议是用接触空气面积比较大的容器来养最适合；因为水蚤会浮到水面上来有类似呼吸的动作，所以若是数量多的时候怕有些争不到位置而死去~~~
光源；一般告诉饲养者，只要有光线就可以了，那....晚上呢?不就全沉到底下去了? 没错，就是沉到下面，结果隔天就死了大半，为什么?因为它们懒得呼吸啰~~~所以，建议是光源不可在晚上也关掉，可以用个小光源(例如5w的小夜灯等)照 着，这样就可以避免这个麻烦。当然有人会说，一定要这样养吗?答案是不一定，不过，要有超多的数量这样是有其必要性的，我们养它不是只有养好玩而已，重点 是要那锅数量，数量够才能喂鱼嘛，对吧?
喂食；一般坊间告诉饲养者，用 酵母粉泡水来喂食，但是若是用量控制不好，水质很快就恶化，造成水蚤快速死亡，那又就要重买水蚤或是再跟别人要啰~~~所以，我的方法算是可以预防这个 吧，同时，也不用太计较去买酵母粉，因为有时候酵母粉不好找，不然就是好大一包，用也用不完，因为我后来想想，酵母粉泡水给它们吃，那是不是只要溶于水的 液体就可以喂呢?答案是肯定的，因为圆水蚤是滤食性的生物，所以一般以滤食水中的营养物来维生，因为我们丢下去的东西若溶于水，它们就吃得到喔~因为，大 雄试了“羊血”(特别感谢小丘热情赞助)来喂食发现效果不错，后来又听说之所以用酵母粉，是因为里面有一些氨基酸类的东西，而水蚤可以吃这个，至于氨基 酸，我弄不到，只好用鲜奶啰~~~相信也有不错的效果..........
日常照顾；其实也不太用理它们，只要给予光照、一些喂食，就可以了，至于换水的话每次吸出水蚤后，再加入被抽掉的水量就可以了~~若是藻类太多，放一些 苹果螺也不错喔，至于效果，嘿嘿那就要看倌们自己试试啰~~~~至于喂食的量，一次不能太多，以一次...2~3cc就可以了~~~别认为太少了喔，这样 就够了同时也不会造成水质一下就恶化了。至于滤水蚤，这比滤丰年虾好用多了，若是不想滤的话，可以用它的趋旋光性来做，用光照来吸引它们然后用滴管吸出， 再来用大量清水洗一洗，就可以拿来喂了。若是想让它们更营养，在喂食前，再喂一些营养液，过一到两小时，再来喂给鱼吃，呼呼这样子更营养啰~~~~
滤水蚤。一般我们觉得水蚤够多了，就可以拿来喂食，而由于水蚤有趋旋光性，所以我们在滤的时候，可以用这个特性，将它们吸引到角落，然后再用风管去吸 取。吸出的水蚤，多半又参有原来水蚤缸的脏水，为了避免污染了鱼缸，所以还要做一个滤的动作，可以用细网目的网子，或是化工材料行买的“生物滤网(300 网目的)”来滤，滤完后再以清水浸泡，或是加一些料(牛奶、维他命等等)然后，就可以间接地使鱼鱼吃到这些东西啰
水蚤的采集和培养
从河里采到水蚤后，应放在较大的玻璃缸里。缸里应放一些从河里带回的水和绿藻，如水绵等，以便增加水中的氧气，还要放一些由蚯蚓、蝗虫或其他动物制成的 碎肉，作为水蚤的饵料。在水蚤数量增加时，要及时采收，并晒干。到了秋末和冬季，水蚤的繁殖力大为减弱。当冬季，在水缸中看不见水蚤活动时，千万不要把缸 里的水倒掉，因为这时它们都潜伏在绿藻丛中。我们可以把水缸放在向阳房间或暖气片附近。到了春季，室内温度升高时，水蚤又出来活动。到室温上升到28℃以 上时，水蚤开始大量繁殖。水蚤可用于饲养教学上所需的水螅。
Cultivate Daphnia
Housing: They do well in a tallish container like a plastic bottle with the neck cut off. Put a little soil or old compost in the bottom. The soil adds a few plant nutrients, salts and food for the daphnia. Then put in some tap water that has no Chlorine (let it stand for a day or so) or use clean creek water. The Daphnia will grow to about 3 mm. Every now and again top up their water with some fresh water. If they start to multiply well put a few into a new container. It is better to use several smaller containers so you won't lose the lot if something goes wrong.
Feeding: Feed then yeast or single celled algae or a little left over liquid from some vegetable soup. Make up the yeast by adding a little dry or frozen yeast to some warm water with a little sugar. Let the yeast multiply for a few hours then feed a little to the Daphnia. They also might like some single celled algae that often thrive in containers left outside. If the daphnia are feeding you should notice some darker colouring through the length of their gut. Because they need Calcium to build their shells, add a little crushed eggshell to the water.
Breeding: Most of the time daphnia produce live young that are just miniatures of the adults. If there are young then you know they are thriving. Sometimes particularly if water quality decreases they make eggs that you will see under the carapace along the daphnia's back. They will shed these off and the eggs will rest on the bottom. The eggs are tough and hatch when conditions are favourable.
Handling: Daphnia can be moved using a large diameter tube with a bulb like a large dropper. Or, pour some water out through a fine strainer then tip them back into a new home. They have to be handled gently because they can get air under their shells and will then float.
written & compiled by
John Clare, B.A., Ph.D.
There are many different species of Daphnia and closely-related genera. However, those of main concern to the aquarist will probably be Daphnia pulex, Daphnia magna, and the various Moina species. Moina are very tiny Daphnids and are often used as an easier-to-culture substitute for Artemia (brine shrimp) as fry food, because young Moina are only slightly larger than newly-hatched brine shrimp, and first stage daphnia are not much bigger. Identifying Daphnia species accurately is best achieved using their size, the shape of the ephippium, the shape of the rostrum and whether the post-abdominal extension is long/short and/or whether smaller appendages close to it are setose (covered with small hair-like structures). It should be noted that within each species there are usually different strains, some of which may have different traits to the "norm".
Daphnia pulex - Although a species in its own right, D. pulex is very hard to distinguish from a number of closely related forms (some consider them seperate species, others sub-species, since hybridisation is common. One example of this is D. galeata). Generally, it is like a smaller replica of D. magna, and is usually fed to the same size of fish. The strain which I culture and know as D. pulex (from the F.B.A.'s 1966 Key to British Cladocera), tends to be larger than that described by many texts (such as that by the British Columbian Resources Inventory Committee), but it is this latter variety which I have found in the wild and identified as D. pulex. I obtained my Daphnia pulex strain from a local aquarist shop only because it happened to come in on some plants. The males are usually 1.5 mm and females 2.5 - 3.5 mm, but the generic D. pulex is taken to have males of about 1.3 mm, and females up to 2.2 mm. Other than the size difference, the two species are almost exactly the same in appearance. D. pulex's colour ranges from yellow to almost red, and in this respect can be very similar to D. magna. The are a number of ways to distinguish D. pulex from D. magna. These include D. pulex's smaller size, one of the appendages of the carapace near the post-abdominal is setose, the ephippium is more triangular than D. magna's and the embyos in it are not parrallel, and there is only one extension from the top edge of the ephippium. D. pulex produces ephippia quite readily in bad conditions.
Daphnia magna is the species normally associated with the name Daphnia by most aquarists. It has been a favourite live food source since the hobby began. D. magna males are 2 mm in length and females are 3-5 mm. They range in colour from a pale yellow to salmon-pink, often this is affected by their food source. D. magna has a wide temperature tolerance, but its optimum temperature is between 18 and 22 oC (64-72F). In the wild, Daphnia magna is quite rare, but where it does occur, it is usually very abundant. Like all Daphnia spp ephippia, the ephippium of D. magna is shaped like a saddle. However, the embryos inside the ephippium (of which there are usually two in Daphnia species) are parallel, and it is like a curve-edged rectangle, with the top long side having two extensions beyond the rectangle at either end. Although magna does produce ephippia, it is less inclined to do so than D. pulex. D. magna is usually considered more "delicate" than D. pulex and as a result it is not as tolerant of culture fouling as D. pulex.
Moina spp are, although similar to daphnia and other members of the Daphniidae, is quite distinct from the genus Daphnia. They are very small in comparison to most Daphniidae (less than 0.5mm in length), and their young are only about the size of newly-hatched brine shrimp. However, their culture is almost identical to that of Daphnia, and although they are harder to acquire, their use as a cheap alternative to brine shrimp as a first fry food has made them popular with many fish breeders.
Where can I culture them?
Daphnia are undemanding in terms of what you culture them in. I personally culture them in 4 (3.4 US) gallon plastic crates because I don't have the space for multiple aquaria. Many people like to use children's blow-up paddling pools (I've used these in the past with great success), but what you keep them in is really up to you. There are some things to bear in mind though when selecting containers:
Is the container made of a material that won't dissolve in water, and/or leech chemicals into the water (some plastics, particularly polypropylene do this)?
If you use a metal container, stainless steel is the safest because many metals will react slowly with water over time (e.g. Aluminium oxidises to form a skin of aluminium oxide, but small amounts of aluminium are released into the water).
Just like ordinary aquaria, it is desireable to have as high a surface area to volume ratio as possible to ensure that there is good gaseous exchange (though not very demanding, Daphnia appreciate a good oxygen supply).
If you're keeping the "tank" outside in strong sunlight or with heavy illumination around, it is a good idea to use a container larger than 10 gallons as the water temperature will fluctuate less markedly, thus providing greater stability for the culture. It is also important when putting a container in strong light that it isn't a dark colour (especially black), because as you probably know, dark colours produce more heat in the light than white or yellow containers.
For someone who only wants a modest amount of Daphnia per week, cultures can be maintained in two litre bottles. For an aquarium, a light bulb in the lid which is on a timer makes it easy to keep indoors (you can get timers from electrical shops or from good aquaria outlets). I have found that Daphnia magna likes gentle aeration. In theory this would seem to be a good idea for all daphnia as it not only helps increase gaseous exchange at the surface of the water, and it also helps stabilise the water conditions and acts against culture-fouling. However, I have found that although Daphnia pulex does better with aeration, very gentle aeration seems to be the key. Airstones should be avoided, since fine bubbles can lodge inside the carapaces of daphnia, floating them to the surface and also preventing them from feeding, and eventually resulting in death (Artemia also suffer from this problem).
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This is a general section on feeding Daphnia. I have summarised my own experiences at the end of this section. Daphnia have similar feeding habits to other tiny crustaceans (especially to the likes of Artemia). The best foods for culturing are algae (typically free-living green algae species which tend to turn water to "pea soup"), yeasts (Sacromyces spp, and similar fungi), and bacteria. Combinations of the above seem to have the most success (i.e. yeast and algae seem to compliment one another). Each food type will be discussed in turn, together with its advantages and disadvantages, and means of attaining/growing it.
Algae
Micro algae is consumed in great quantities by Daphnia, and the abundance of daphnia is usually proportional to the density of algal blooms. There are a number of ways to grow algae, all of which are very basic and require little effort.
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Placing a container of water outside in good sunlight will usually guarantee a good growth of algae within two weeks, usually a lot less. Algal spores are carried on the wind and will colonise the water, but it usually speeds up the process if you "seed" the water with some algae from a container that has already has a bloom.
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Miracle grow, an organic plant fertiliser, can be used to grow algae (after all they're just plants). One method is to use 1 gallon containers, 1 for each day of the week. These sit on a window sill which gets good sunlight for as much of the day as possible. By bubbling air through the containers (an airpump with 7 side lines will do, because there really only needs to be a small movement in the water), algae won't grow on the sides of the containers where it can block the sunlight. Add 1 tea spoon of Miracle grow per gallon. This system is then seeded with green water in tank #1 - two days later tank #2 - two days later tank #3, etc. When this has turned bright green (within 2 weeks), pour it into a Daphnia tank. Refill the container with water mixture and seed with tank #2 which should be about to turn bright green. This is repeated with each container as they turn bright green. As you might be able to tell, this will provide about 1 gallon of fresh green water every two days.
The advantages of algae as a food are that it is very easy to culture and it is excellent for growing daphnia. There are no disadvantages really, other than the fact that it requires bi-daily maintenance / renewal.
Yeasts
There are two general kinds of yeast that we need be concerned about - activated and inactive. Activated yeast is generally a better food to feed because it will not foul the water as quickly/as much as the inactive kind. Bakers, brewers, and almost any kind of yeast are suitable for daphnia cultures, but it is recommended that no more than half an ounce of yeast per five gallons of water be fed every five days. If you're using yeast, especially inactive yeast, consider adding some algae to the water as this will counter any fouling which may result from adding the inactive yeast (this isn't so important with activated yeasts). Do take care not to overfeed inactive yeast as it will foul the culture and therefore kill your daphnia.
Some bakers yeasts come with added ingredients like Calcium Sulphate and Ascorbic acid (vitamin C) to aid fast activation of the yeast. These are harmless to daphnia cultures, but care should be taken when adding this kind of yeast because Ascorbic acid can give pHs less than 6, which are far from ideal with Daphnia. However, I have never had any pH changes when using such "mixes" in moderation, and the calcium sulphate gives vital calcium for the daphnia's carapaces.
The advantages of yeast as a food are that it's easy to acquire, and there is a minimum of fuss when preparing it for the culture. The only slight disadvantage is that it's not quite as good a food as algae (the daphnia need to consume more weight of yeast than algae to get the same food value). However, yeast is far better than any other food except some bacteria, which have almost as high a food value.
Bacteria
Bacteria have a similar food value to fungi, but they generally reproduce faster than fungi and algae, although the food value doesn't tend to be as high. Bacteria are "cultured" by taking 5-6 ounces of dried horse, cow or sheep dung (dried for two reasons: it's easier to deal with, and most antibiotics or growth promoters which were fed to the animal will break down if the dung is left to dry for a while) and tying it in a nylon bag (such as tights/pantyhose), and hanging this in the water with the daphnia. Animal dung (including human dung, though don't use human faeces unless you want typhoid or worse...) contains copious quantities of bacteria from the digestive system, and these will leech out of the dung into the water and reproduce. Typically, the water will go cloudy after a time, indicating that the bacteria are starting to multiply. This should be changed once a week for maximum effect. Another method is to soak the dung for weeks until it decomposes into a nutrient slurry, then drip the liquid into the tank at a rate of 16 fluid ounces per five to eight days.
Another way to culture bacteria in a hurry is to throw a handful of salmon (or trout pellets), dog biscuits or other meat-based food into a few gallons of water with some added aquarium water. Within a few days it is usually cloudy with bacteria.
Bacteria are a good food source, and easily acquired/cultivated. The only downside is the smell of the decaying matter (which can be pretty bad at times). An important thing to remember is that horse dung usually contains tetanus (also a bacterium), so care should be taken when handling it (make sure you have no open cuts/sores on your hands or arms).
Other FoodsThese include bran, wheat flour, and dried blood. These should be considered similar to inactive yeast, and the same amounts and care should be taken when administering them. The only real difference is that the food value isn't as high as the corresponding weight of yeast.
Some of My Own Experience
Unless you have a very large container, like an outdoor pond, I don't think "green water" is worth the effort. I fertilise the water with salmon pellets (the Indiana University Axolotl Colony's at the moment - May 2000). The amount depends on your container size and current daphnia population. Too much and you foul the water and everything dies. As a guide, I would say for a 4 foot long aquarium one or even two handfuls is enough to fertilise the water if there is an already healthy population of daphnia. If you have less, then don't use as many pellets or the bacteria population will go out of control. this is reliant on temperature, ideally in the early 20s celsius / ~70F.
People recommend green water as the best food for daphnia. I would have to say that I mainly agree with this, but I think that bacteria are just as nutritious. I haven't bothered feeding green water to daphnia since 1998 so draw your own conclusions. I've been maintaining two populations since June 1998 and they have never completely died out. They do pulse though. If you want a recommendation for a quick fix substitute for green
water, get yourself a bag of frozen peas and one of carrots. Mix about 80% peas and 20% carrots together and then stick them in a food blender. Blend these until you have a mulch. You're looking for the "juices", so take any liquid and squeeze the mulch to get all of the liquid from it. This contains particles of a size small enough for daphnia to sieve from the water (less than 50 microns). It's far more concentrated than water with algae in it, so use it sparingly. It gives just as good a result. I've used this a few times, but I'm just too lazy most of the time to bother with anything except rotting pellets.
One final note on pellets - don't crush them much first. If you do you'll release all of the nutrients at once instead of over a few days and you can get the bacteria going out of control. I should mention that I also keep water slaters (the European fresh water louse) in my daphnia cultures because they break down solid waste and prevent the pellets from being covered in fungus and floating at the surface. The fresh water louse is a crustacean
that looks like a wood louse and it is not a fish louse (louse is just the name). I don't recommend snails in the culture either because for one thing, some species can act as a parasite vector, and also because they use up calcium and that's reserved for the daphnia! I've heard of ground-up liver in water being recommended. In that case it's mainly the blood that is the fertiliser. I've tried animal's blood and found it ok, but the pellets win in my opinion, followed by algae and the mixture I mentioned above.
Daphnia production is relatively simple, if not an exact science. However, there are proven measures that increase the productivity of a culture.
Good aeration (good in so far as the manner in which the water is aerated, not good as in quantity) is probably the largest contributing factor for good production. Some species prefer no aeration, but Daphnia magna seems to do well with it. It allows you to keep more daphnia in the same container. It also circulates the water, (which counters stagnancy and fouling). It minimises the possibility of algae growing on the walls of the container, and it also keeps inert food in suspension which is more conducive to most daphnia feeding habits. The only problem with aeration is that fine bubbles can lodge underneath the daphnia's carapace and float it to the surface and preventing it from feeding. Therefore airstones should be avoided (unless used in a bio-foam filter in which case the air bubbles combine together), or coarse airstones (or better yet, no airstones) should be used instead.
A good method (tried and trusted) of aerating the water which I have mentioned previously is the bio-foam filter (there are a number of models available, any will do). These are commonly used in fry tanks, but are ideal for daphnia. They trap larger particles in the water (they don't trap algae), and help break them down, releasing nutrient for the algae to feed on. The outlets are usually very good at aerating the water, but care should be taken to use them at low to minimum flow to avoid over-agitating the water (we want some aeration, not a torrent). I haven't had a fouled culture yet while using a bio-foam.Carry out regular maintenance as described in the Maintenance section, especially water changes.
Cull/Harvest the culture regularly (again, see the Harvesting section). This encourages constant growth and also keeps the daphnia from exhausting both the oxygen and the food in the water too fast for it to be replaced.
Some people like to keep a light on 24 hours a day for their daphnia tank as this can encourage faster growth and reproduction. I haven't tried this myself. However, you probably won't need to do this once your culture gets going. One important note though - continuous 24 hour periods in which the daylight is less than 12 hours and with a temperature significantly below 18
Water changes: some people recommend you change up to 75% of the water in a culture every day. This is really dependent on what rate you're "running" the culture at. The more food you feed, the faster the water will be fouled, and therefore the more frequent the water changes. This is really up to the individual, but be aware that output levels will drop if there is a build up of metabolites/toxins/etc in the water. This could lead to crashing.
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This section is intended as a reminder of things to remember and a precaution against simple mistakes people often make without realising it.
DOs
Do make sure you age your tap water and have a good idea of what's in it:
If it contains chlorine (chloramine will also put chloride into the water), it must be left to stand or aerate the water for 24 hours to drive off the chlorine gas (fluoride is usually very low in concentration and isn't really something to worry about).
If your water contains lots of ammonia, this will inhibit the population growth of your culture - again, aerating the water vigourously helps drive off ammonia (although it takes a lot longer than with chlorine).
Any metals in the water can often be toxic to daphnia. Some can inhibit population growth (see the section on Physical Requirements).
Do carry out regular partial water changes.
Do feed regular modest amounts of food (this will depend on the culture size).
Do make sure you have adequate water hardness for your daphnia, otherwise they will not reproduce at a high rate, and will probably just produce ephippia.
Do try to maintain a constant temperature (about 20oC is ideal for most species).
Do cull/harvest your cultures at least once a week to avoid overcrowding.
DON'Ts
Don't wash your hands with soap/detergent just before you put your hands in a daphnia culture unless you've _thoroughly_ rinsed your hands because soap and detergents are toxic to daphnia.
Don't overfeed - if anything, underfeed your daphnia to avoid fouling and toxic build-up of ammonia.
Don't put your daphnia in a container of dense algae (and don't change too much water from the tank for algae water at one time) because algal blooms tend to raise pH to very high levels (over pH 9), and coupled with even a low ammonia concentration, this could be disastrous for the daphnia, killing them in short order. Ammonia toxicity increases with higher pH.
Don't keep all your eggs in one basket (or daphnia in one container). Even the best of us will have accidents on occasion or have an emergency, etc, and our cultures may be poisoned or die off for no apparent reason. To counter this, it is best to seed as many water vessels, aquariums, and even flower window boxes with daphnia when the culture is first obtained. This will ensure you will be able to "restart" without too much fuss.
Don't use insecticides near your daphnia containers, and don't leave your daphnia container in a room that was just painted/varnished/etc, because the fumes/gas can be toxic, and even if it doesn't kill the daphnia, the fish you feed them to may be slowly poisoned.
Don't use airstones in a daphnia culture. Use an open airline tube or a bio-foam filter (the latter contains an airstone inside in the apparatus, but the bubbles are not fine enough to harm the daphnia when the bubbles emerge into the tank. Note however, there should only be a weak flow of air through the filter to avoid too much water flow).
Don't add miracle grow, etc, directly to the culture. It won't be much use, and it could also poison the culture, in high concentrations.
Don't add fresh tap water to a daphnia culture unless you want to kill them all with the chlorine.
Don't keep your daphnia in the dark for days at a time as this can stimulate them to produce ephippia.
