Originally used as a cure for malaria in the late 19th century, methylene blue has since become a staple preventative within the fish keeping hobby. It has many practical uses that make it one of the best medications to have on hand. But it also has it’s quirks. It’s essentially a dye, so anything that it touches will be blue for eternity. This includes silicone, tubing, filters, your carpet. However, once you learn how to wield methylene blue, you will become an unstoppable force that’s able to raise more fry than you’ll be able to handle.
Methylene blue is a great fungus preventative when it comes to rearing eggs. As someone who raises killifish eggs, this has become extremely important since killifish do not display parental behaviors and the eggs need to be removed from the spawning tank. This is a necessary step in order to prevent predation when the fry hatch.
As for the dosage amount, there doesn’t seem to be a hard and fast rule about how much methylene blue to add to the water column. Some breeders use a paltry drop per gallon, heavy-handers use 10 drops per gallon, while others simply go by color. I’m a fan of the latter. I put just enough of Fritz’s Methylene Blue in my fry hatcheries to give the water an nice, even light blue coloration. This has helped the hatch rate of my fry tremendously! Without using methylene blue, I struggled to produce a handful of killifish fry from 20+ viable eggs. Now that I’ve introduced methylene blue into my routine, I can easily get an 85% hatch rate.
Regardless of the concentration of methylene blue of you choose, be prepared to perform a water change on the day that the eggs have hatched. The hatching date will always be determined by the species and the incubation time. If you have any success with certain concentrations of methylene blue, let me know down below or use the contact form in the menu above to email me!