mandag den 7. januar 2013

Live food: Hyalella azteca (Scuds), breeding and using as fish food

Hello all,
So one of the most interesting aspects of keeping fish, to me at least, is when they exhibit their natural hunting behaviour. And they do not really do that when we only feed them dry flake food. And although flake food (probably) contains all the needed nutrients etc, nothing really compares to the content of live food. And when you feed your fishes live food you'll also get to see them hunt throughout the aquarium, searching and swallowing whatever they find. This makes for much more active fish, and thereby a much more entertaining aquarium. And when you add the bonus of the fish exhibiting much more bright colouring and general health, I really find nothing beats live food.
As it happens it can also be almost as interesting caring and breeding this food.
So all in all, I find it to be a natural choice to have some means of providing live food at least once a week.
I've several different types of live food, but one of my favourites is the Hyalella azteca, (also known as Scuds and Mexican freshwater fleas). These contain tons of nutrients and are also sufficiently difficult to catch that the fish will really have to work to get their food.
And they are also very fun to observe and very easy to breed and feed to your fish.

The following is how I maintain and use these little crustaceans, but I guess there is many more possibilities.
Two years ago I bought a small group of azteca from a seller on Ebay. And for a while I had almost given up on the little buggers as they didn't really grow, nor, did it seem, multiply.
I then turned to the following set-up which now provides an abundance of azteca - fully enough for a weekly feed.

The setup is basically two medium plastic containers (bought by my wife, intended to hold the children's toys, and cost about 5$ each). These are ca. 20 litres and large enough to hold to healthy colonies.
In each of these I've provided some cover - bits and pieces of hose pipe, some Leca pellets and whatever I had lying around that I deemed was safe to put in. The idea is simply to provide some cover for the scuds to live in.
Each of these tanks are unheated (averaging about 17-20 degrees depending on season), have no lighting (although they get a moderate amount of indirect sunlight) and are unfiltered. They get a small amount of fresh air each day (ca. two hours) through an air stone set to a moderate amount of bubbles.


Hyalella azteca set up 1
In one of the tanks I've added a lot of long green algae that I found behind one of my filters (it had direct sunlight and produced a lot of this stuff). The Scuds seems to love living in this.
Hyalella azteca set up2
In the other I deposit the filter wadding I use in my filters. I guess you could add new, shiny cotton wool, but instead of throwing the dirty filtergoo out I've experience with using this as food for the azteca. 

Which brings me to how I feed these little buggers. Contrary to what I've read, they do not seem to be interested in eating plants. I've tried starving them and providing various types of living and dead plant leaves, vegetables etc and they seem generally uninterested in this type of food. What they really do appreciate (at least judging on their reproduction speed) is filter goo, sinking pellets intended for catfish, and dried fish food. Whenever I give them this type of food I'll see it quickly attacked by the scuds and quickly devoured.

 A small group of very active and healthy azteca, ready to become fish food :-)

When it comes to using them as food, I normally just take one of the wads of filter wadding they live in (or a piece of the algae) and throw it in the fish tank. This results in most of them instantly trying to escape, much to the enjoyment of the fish who will hunt them. The rest will stay within their  cover, which gives the slower fish a chance to 'graze' through the wadding, where they will stay for hours hoping to pick out a straddler or two. Afterwards the wadding or algae just goes back into the azteca tank.
I estimate a few survives each feeding, meaning most of my fish tanks have a healthy colony of azteca living in them, but I see this as a bonus. This provides a natural source of food within the tank, and the azteca should provide a health bonus by removing uneaten food and other goo. If you fear to have a living colony inside your tank, you could just collect the azteca (hold the wadding above a small tray and they will quickly drop into it) and let them die from lack of water (barbaric, but considering what their fate is I guess we shouldn't judge :-)).

This is what Wikipedia has to offer on azteca:
Hyalella azteca is a widespread and abundant species of amphipod crustacean in North America. It reaches 3–8 mm (0.12–0.31 in) long, and is found in a range of fresh and brackish waters. It feeds on algae and diatoms and is a major food of waterfowl.

All the best,
Kasper

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