Originally Posted by
Willie
Discus eggs cannot be fertilize in hard water because calcium ions signal the membrane to change fluidity and block fertilization by sperm. In soft water, the egg secretes calcium ions to signal fertilization and block further sperm entry. However, this is the ONLY time when discus cannot survive in hard water.
The solution is quite simple. Put your fish in the 29-gallon breeding tank with hard tap water. At some point, they will start to clean the substrate in preparation for spawning. At that point, change out 50% - 75% of the water with R/O. You can purchase 20 gallons of R/O water from most LFS for $0.50/gal. The fish will lay eggs in soft water and the eggs will be fertilized in soft water. The spawning process typically takes 45 minutes. Afterwards, you can proceed with normal water changes using hard tap water. The eggs will hatch fine, the fry will go free swimming, attach to the parents, etc.
In the entire life cycle of discus, it only requires about 45 minutes of soft water. You can purchase an R/O unit or just buy some 5 gallon water jugs.
Good luck, Willie