Norm's "Hands-off" Hatching Method
by Norm Ruebsamen

After struggling over the years with hatching eggs collected from certain Killie species, I have come to realize that there are certain fish eggs which just can’t be handled. This is undoubtedly one of the reasons a fish gets the label “difficult to breed” or “challenging”.

One of these fish is Rivulus obscurus, Rio Purus. I have found that it is futile to collect eggs by hand and put them into containers. Simply touching the eggs seems to damage them. I have tried different hatching solutions and also placing them on top of peat. Some eggs will eye-up but most will not hatch even when force hatched. My only success was with the few fry that showed up in the tank with the parents but the number was very small.

I wanted better results and think I have finally found a solution. Now I lift the mop and place it in a sealed zip lock bag bringing some of the water with it and being careful not to squeeze the water out of the mop. In about 16 days, or after the incubation time is up, I place the mop in a shoebox of very green water. The first time I tried this I had nine fry hatch, 5 the first day and a few more as the week went on. There were probably twelve to fifteen eggs in the mop when I started so I was very happy with a 60% hatch rate. It seems that sometimes the simplest methods work the best.