Breeding Discus Fish 101

by | Nov 19, 2021 | 4 comments

Gabe Posada: My number one phone call is when people call me up and say, “Hey, Gabe Posada, I need a male discus because my male is shooting blanks. The female spawns constantly, but the eggs go bad. So I have to assume that the male is not doing his job, the female is doing her job, the male is not doing his job.” This article will help to remove errors and other reasons why the discus eggs are not hatching. In this article, we will discuss how water chemistry is essential for breeding.

It’s All In The Water (pH and conductivity)

If Your Discus Fish Are Laying Eggs, You Have A Great Tank Environment.

The fact that the females are laying eggs means that the environment is perfect for them and they’re happy, and congratulations to you if you’ve achieved this! The fact that they are laying eggs that are not hatching, though, means that the water quality needs to improve. So we use reverse osmosis water here in our discus hatchery.

City Water And Reverse Osmosis Water

Now, what’s the difference between city water and RO water? City water comes in with chlorine and chloramines, which most of you take out with your de-chlorinator, or you let it age in a holding tank until the chlorine and chloramines dissipate. It does contain minerals, calcium, all the kinds of stuff that has to be in the water. The municipal water companies are pulling it out of the ground, and it does come up with minerals.

Osmotic Pressure

Those minerals create osmotic pressure and increase relative density, which is why you float in saltwater and sink in freshwater. The osmotic pressure created by the minerals in the water will make the eggs calcify. As a result, your discus eggs turn white very soon after the pair spawn.

When there are higher levels of minerals in your water, the pressure outside the eggs is less than the pressure inside the eggs. As a result, the Osmotic pressure draws the liquid from the discus egg, and the discus egg becomes calcified. Your discus eggs will not hatch with hard water. You need to use reverse osmosis water.

Low pH Does Not Always Equal Soft Water

I know that over the years, people have called me and told me, “Gabe, my water is soft because my pH is at 6.5.” Let me explain something to you. pH is just letting you know what the acidity or alkalinity of your water is. Your pH is not telling you how hard or how soft your water is. You see, you can have very hard water with a very low pH. You can have a very high pH with very low conductivity.

So, if you start breeding discus, you need to purchase a good pH meter. I strongly advise you guys to get a pH meter and a conductivity meter so that when you call me and ask, “Hey, why aren’t my eggs hatching?” the first thing we are going to ask you is, “What’s your conductivity, and what’s your pH? These two measurements are essential.

I’m going to show you the meters that we use and how to calibrate them. I’m going to take you through the process step by step so that you can get those eggs to hatch. I realized that most of you want to see it for fun. So I’m going to be the first to raise my hand and tell you that it changed my life when I got my first batch of discus eggs to hatch for the first time.

Get A good pH Meter And A Good Conductivity Meter

We carry both of the Milwaulkee meters on our website in the Equipment Products.

We will talk about how to calibrate the pH meter and the basic pH levels for discus breeding. We are also going to be talking about the conductivity meter, how to calibrate it, and the basic levels of conductivity you need to get discus eggs to hatch.

Calibrating the Milwaulkee MW101 pH meter

In this section, we are demonstrating the Milwaulkee MW101 pH meter. Any pH meter will do, but make sure you get a decent one. The MW101 is portable, battery-operated, and hand-operated.

Now what you’re going to find is your calibration screwdriver. You’re going to find your probe, which comes with a bootie on it. It comes with a protective liquid, like a storage liquid, so the probe doesn’t run dry.  The probe gets plugged directly into the unit through a BNC connector.

Once you’ve rinsed off that storage solution, you’ll be ready to calibrate your meter. Fill up the two calibration liquids, the 4.01 and the 7.01. You’ll notice immediately on the display that right now, it’s going down into the fours because it wants to calibrate. Now on the side of the unit itself, you’ve got a calibration of 4/10 and a calibration of 7.

Once you have put the probe into the 4.01 calibrating liquid, stick the screwdriver into the four of your calibrating four and turn it slightly. If you turn it to the left, it goes up. If you turn it to the right, it starts to go down. Adust the screw until your meter reads 4.01 pH like the calibration. That would be your first calibration.

To begin your second calibration, rinse the probe one more time in regular water and dry it off before placing it into the 7.01 solution. You’ll notice that the meter is already reading.

Adjust the calibration screw until your meter reads 7.01. Now, this meter is calibrated.

This meter will read both reverse osmosis water and city water, but remember, if you’re using your calibration liquid, those little liquids are designed to read the minerals in the water to determine what the pH is or the buffers. When you’re using reverse osmosis water, there are no buffers. You need a digital one to get an accurate reading. Now this meter is calibrated.

(for a more visual explanation of calibrating the MW301, watch the Breeding 101 video above)

Why is pH important to breeding discus?

When I test my breeding water, it varies because there are 78 breeding pairs, and we feed heavily and stuff. When you use pure reverse osmosis water, the drawback is that there are no buffers in the water, so your pH tends to go down.

The way we remedy this is to add sodium carbonate, which is the same product used to raise the pH of swimming pools. We use one teaspoon per 1,800 gallons to stabilize the pH. If you only have one or two tanks, you may only require whatever you catch with your index finger. Just dissolve it in a cup of water and put it into your tank. You won’t need much.

PH is important because if your pH is lower than 5.5, the acidity will kill the sperm of the male, and the eggs will never fertilize. So you want to be above 5.5. I know that the lower in PH you go, the less bacteria in the water, and that is true. When you have more acidity, you will get less bacteria. Bacteria can’t tolerate low PH, but it’s a fine line between fertility and lower bacteria.

You want to be above 5.5. Anything about 5.5 to 6.5 is ideal. Anything above 6.5– Then you start running into problems with fungus on the eggs. You begin to run into problems with bacterial attacks because the higher the alkalinity, the more bacteria you build up. Now, remember when you’re breeding, you’re doing water changes every day practically because you’re removing all the debris from the bottom, all the uneaten food so that it doesn’t decompose and create a problem for your fry. We have to have pristine conditions.

This is only for when you are breeding discus, which has nothing to do with keeping discus. Remember that when I say water changes daily, I am talking about breeding. I’m not talking about keeping discus; let’s not confuse one with the other. The biggest fallacy I hear constantly is how you have to do water changes every day when you keep discus. If that were true, I wouldn’t even have a fish tank at home because I wouldn’t have the time.

This is just for breeding. Every day you get in there, you siphon out the little pieces of fecal matter or uneaten food. You don’t even have to fill up the tank because you probably pulled out a cup if you do it every day. All right? At the end of the week, you fill the tank back up.

Now the pH is crucial because it will determine whether your eggs and baby discus are going to get attacked by bacteria. If it’s too low, it’ll kill the sperm from the male, and it won’t let the eggs fertilize.

Your pH meter is your left hand, and your conductivity meter is your right hand when you’re breeding discus. It took me a lot of money and a lot of time to figure this out. Now we’re going to talk about your right hand.

Calibrating the MW301 Conductivity Meter

Now we’re going to calibrate the MW301, which is your conductivity meter. The conductivity meter also comes with a calibration solution. This device also has the same calibration screw and the same screwdriver. The way this is calibrated is to use the 1413 solution, which comes with the unit.

First, hook up the probe. This probe is different because this one has two electrodes in it, which determine conductivity.

Put the two electrodes into your 1413 solution, and adjust the dial screw to correct the calibration.

What is conductivity?

The conductivity of water is determined by the quantities of minerals dissolved in it.  When minerals dissolve in water, they break apart into ions. These ions are what increase the electrical conductivity of water. When discus eggs are made, they have a very low mineral content. If that content gets too high, the eggs will not hatch. If there are more minerals dissolved in your water than are in the eggs, the minerals will pass through the semi-permeable membrane of the eggs and calcify them. Conductivity tests the ion content of your water, which tells you the mineral content, which will be what makes the eggs hatch or not.

Now when you test your water, there are a lot of meters out there. You can do a TDS meter, you can do a PPM meter, or you can do a conductivity meter. Basically, they all read the same thing; they read general hardness. Here at Wattley Discus, we test only the conductivity of our water. This is why I recommend getting a meter that tests conductivity: so that when we communicate, we’re both using the same measurement. If not, it will be up to you to convert your PPMs or TDS into microsiemens so that we’re on the same playing field.

Testing various water samples

When testing my water, the meter tells the level of conductivity in micro siemens.  If I were to put the two probes of the MW301 Conductivity Meter into my breeding water, it would tell me it is currently at 61 or 62. Now inside the breeding section, it’s 61-62 because

we feed them beef heart, and as you know from looking at the formula on my other videos, we use multivitamins. Whether they eat it or don’t eat it, the multivitamins have minerals in them, and they’re going to melt into the water.

Let’s say that I wanted to try using straight well water for a test. If we used regular well water in our breeding tanks, you would see why the eggs would never hatch. If I were to test our well water

before filtering it, it would read 514 or 515 microsiemens. The well water has mineral content that is more appropriate for breeding African cichlids; we’re not going to breed discus. Your city water probably runs between 250 and 275, and it’s still too high. You want to be between 35 and 80 microsiemens maximum so that you get the most amount of eggs to hatch.

While I was over there getting the well water, I also walked by the RO water holding tank. I want you to see the conductivity level that our holding tanks are. This is pure RO water. The industrial units, this is what they produce: 22.

We use this water to bring down the conductivity of our breeding water, but one could also use deionization or various other methods. Otherwise, these eggs will never hatch; it has nothing to do with the male being fertile or infertile. If you don’t have the proper conditions, these fish will not breed. I know you’re going to tell me, “Gabe Posada, my Angelfish eggs hatched.” That’s fine. That’s why you can get Angelfish for $5 because anybody can breed them. Discus are a little bit more difficult.


While I was trying to adjust this meter, I noticed a pair right behind me attacking me. I couldn’t figure out for the hell of me why, and lo and behold: we’re talking about breeding discus, and there you go. There you go. That’s what it’s all about. Getting your discus to breed is what this tutorial is all about. So you guys can experience and enjoy what I get to do every single day of my life. I’m hoping that you guys are successful with this article; I’m hoping that all of you write to me and tell me how everything all of a sudden turned around. I know there will be a million questions, and it’s okay; I’m used to it, I’ve been answering them for 25 years, but I’m hoping and praying that this article shows you guys the basics of what you need to do. Then the rest of the articles and videos that we put out there for you will show you the other little tidbits that you need to do to become successful on it.

Thank you from the bottom of my heart, and again, I apologize for not being back so quickly. It’s just that we became overwhelmed with orders, and we’re happy about that because now we’re expanding even more and enjoying the hobby even more. Thank you all. Enjoy. Don’t forget, We’re on YouTube and Instagram. Netflix, not yet. Instagram. We’re all over the place, but we’re here for you.



  1. tgroset

    Great article. Thanks

    • Daniel L. Taylor

      Hi Gabe. I just read your article all Angel hatcheryon FB on ph and hardness when hatching eggs. I used to operate a small Angel hatchery anf my eggs litetally calcified and cracked apart on the slate! NOW I have a better understanding as to why and how this happened


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