D.I.Y. simple fry rearing box

This is a very simple, cheap but effective fry rearing box. This example does not have proper floating supports as it's resting on a root in my tank. Floating support or something to anchor the box to the side of an aquarium would be easy to ad.

What you need: plastic box with a lip at the top to hold some air, silicone, carpet knife, filter foam, and a spare small airlift filter:

A hole was cut at one end of the box and sealed with filter foam, attached with silicone. This will drain the box and keep the water level the same as in the tank it is in. The air driven filter will pump in fresh water from the tank into the box:

Side view:

In tank:

From above:

This is a variation of a design that has been used by aquarists for many years. 

The benefit of this type is that air driven filter constantly supplies the fry/eggs with fresh water from the same tank that they originally were laid in/hatched in. This method also keeps the water conditions stable which is extremely important with fragile fish, something that can be harder to achieve in a small 
separate tank.

Another benefit is that the breeder box makes it easy to make sure that the fry eat, the small space makes it possible to target feed fry while fry in a larger tank might not even find the food in time.

Maintenance of the rearing box is still important though and uneaten food and bacteria on the sides should be removed/cleaned on a regular basis. A turkey baster works quite well for this purpose, and a tooth brush can be used to clean the sides.

Depending on species and strength of the air pump used it can also be a good idea to add an air stone for increased water circulation.

Personally I use this type for plecos and corys; I ad gravel/sand from the main tank, some small plants/moss/roots/oak leafs/ for the fry to hide in.

Remember that we want the fry to feel comfortable and not stressed as this increases their growth rate and lowers the risks of deaths.