The first thing you need to understand is that you are not in total control. If Discus do not want to pair off, there is nothing you can do about it. The only thing you can do is provide the right conditions so that it is more likely that they will pair off.
If you have a sexed pair and they are the only discus in the tank, it is likely, about a 70% chance, that they will eventually pair off if left together for a long period of time.
To hurry our potential young lovers along, we provide conditions that are conducive for fishy love. We put seven mature Discus in a 125 gallon tank and let them acclimate to it for two weeks. We then start doing some sudden changes in the tank conditions to stimulate courtship. Some of the changes we make are:
• Change the water temperature to 78 degrees for a few days and then bring it up to 88 degrees over about 12 hours and then leave it at 88 degrees for the remainder of a week.
• Let the tank get somewhat dirty, not doing the daily water changes for a few days and then doing a 80% water change.
• Feed them heavily for a few days and then stop feeding them for two days, followed by feeding them live food for three days.
• Do two 60% water changes four hours apart where the Ph goes from 6.5 to 7.0 at the first change and then from 7.0 to 7.5 at the second change.
• Leave the tank dark for two full days and then turn the lights on for two full days.
If we have tried all of the above and after two months they still have not paired off, we switch out four of those discus and start the process over again with four new discus along with three remaining.
The spawning process is the pinnacle of Discus keeping. This has always been my favorite part of Discus keeping and I still, 30 years after my first spawn, find it fascinating.
The first sign that your discus are getting ready to spawn will be their obsession with cleaning a rock, or filter tube or side of the aquarium. Once you see both of them doing this, spawning will usually follow within a day or two. You will also see them start doing the mating dance. They will swim towards each other at a slightly upward angle. Once they get next to each other, they will shimmer and then swim away from each other at a slightly lowered angle. The most spectacular aspect of the spawning will be the colors of your Discus. Whatever their color, it will become MUCH more intense and vibrant during spawning. This will be the prettiest you will ever see your Discus. They will also become aggressive toward other fish, including Discus, at this time. They will aggressively defend the breeding site from all intruders, including you.
At some point after your Discus start doing all of the above, they will actually lay the eggs. It will start with the female rubbing her belly, and her breeding tube, against the surface that they have cleaned. She will always lay in an upwards motion. The total length of the spawning run will be between ½ and three inches. She will lay between 1 and 12 eggs per spawning run. The male Discus will usually then follow directly behind her in the same basic motion spraying the eggs. You usually cannot see the actual cloud. The entire process can take between one and five hours.
This is when the fun is over and the frustration can start. The first two issues that you will be confronted with are eating of the eggs, especially by the male, and infertility.
We will now go over what to expect after the eggs have been laid. This is where the frustration starts. The first two issues that you will be confronted with are eating of the eggs, especially by the male, and infertility. We will go over the eating of the eggs first. We will go over fertility in the next part of the series.
The number one problem, and the one you must get past, with breeding discus is the eating of the eggs by the parents. While both parents will eat the eggs, the male does it more often. This is often done as they spawn and there is very little you can do if this occurs while spawning. The female will make her egg-laying run and then the male, instead of following her with a fertilizing run, will follow her and eat the row of eggs. This behavior is most common in new pairs. A majority of new discus pairs will eat their eggs. Fortunately, they will often stop this behavior as they become a more mature spawning pair. If you get lucky and they do not eat their eggs when spawning, there is a good chance that they will eat them before they hatch. Fortunately, if you get this far, there is something you can do. You can, at this point, take the eggs out and artificially raise them or you can take a mesh screen (house soffit screen works very well) and fit it directly over the eggs. This will allow the discus to still blow on the eggs and bond with them, but will keep them from eating the eggs. Obviously, you will need to have planned for the spawning and will need to have created the screen prior to the actual spawn. If the eggs do not get eaten and are fertile, they should hatch out in three days and become free swimming in about six days.