Mass Deaths of L144 Pleco Fry in 10 Gallon Grow Out Tank


New Member
Jan 27, 2020
Mass Deaths in L144 Pleco Fry in 10 Gallon Grow Out Tank

Long Explanation, because I assume to much information is better than too little, so please bear with me.

I am a relatively new fish keeper, about 1.5 years now, and I got into breeding plecos after doing research into breeding projects to try. I fell in love with the “Blue-Eyed, Lemon, Long Finned” Bristlenose Pleco (sold as L144) and decided to try my hand at breeding them. After doing a lot of research, I decided to try to breed them in a 20-gallon long tank with gravel substrate, lots of driftwood, and various plants (different swords and dwarf sagittaria). I bought 6 juveniles online and managed to get 4 of them to adulthood, 1 male and 3 females. To my delight the male quickly claimed one of my two pleco caves and within a month or so, I noticed my first fry in the tank! Content to let them breed on their own, I simply kept track of things, seeing what foods they prefer (carrots, cucumber and zucchini are favorites, they do not like green beans and they LOVE repashy gel food) and noting when females looked gravid or any breeding behavior occurring.

After a few batches of fry, I checked the tank one morning to find that my male had kicked out a whole packet of fertilized eggs. I checked online for ideas of what to do and decided to use the 10-gallon tank I had set up and was cycling next to the 20-gallon to become a potential home for a betta. Using the extra driftwood I had bought for my 20-gallon pleco breeder, I bought some java fern and dwarf sagittaria to make sure I had plenty of surface area for them to rasp and at least some root feeders to pick up the waste in the gravel since I do not like gravel vacuuming with some many tiny fry in the tanks (and have successfully not needed to gravel vacuum in the past with dwarf sagittaria). I set up this 10-gallon tank almost exactly as my 20-gallon: an aquaclear filter, two sponge filters (usually both with an airstone but currently only one has an airstone) just of a smaller size, same kind of woods (cholla, Malaysian, coconut), and java fern instead of sword plants. I put a “Penn Plax Deluxe Net Breeder” box I had under the filter to lightly tumble the eggs, ensure good water flow, and added a few snails, all to ensure the eggs did not get mold on them. Sure enough, a week later little wigglers were scattered about the box and I had babies!

Proud of my success, I waited until their yolk sacs were gone before gently coaxing them out of the box and into the main tank. My male continued to occasionally kick out batches of eggs so I would just put them in the breeder box and repeat the process. I did this three times over two months and a couple weeks ago put my 4th batch of rejected eggs into the breeder box. However, almost a week ago I noticed some dead fry in the tank. I know some fry just fail to thrive/have congenital defects that can cause them to die, so normally this would not worry me, but these were some of my oldest babies (two months old) not the newly hatched ones. I pulled out the bodies, they did have “dark” and round bellies that my fry normally had, so they were not starved, I did a test and the water quality was “perfect” (No ammonia, no Nitrites, 10ppm Nitrates) and no signs of infection, parasites, or other disease so I was stumped. I decided to do a water change and to treat for parasites since I noticed some of the older living babies had a bulging side and did have a lot of detritus worms in the tank. However, the next day I had almost 30 dead, all of various ages, and still no sign of disease.

I have been performing daily water changes, since before I would do only a change roughly every few days once a week to not damage fresh fry and there were only very small fry in the tank and thus not a heavy bioload like the 20-gallon with 4 adults and older fry. However, fry are still turning up dead despite my best efforts to rectify the problem. Note, I feed and treat the 20-gallon tank with the same food and water as my 10-gallon (of course in different amounts due to tank and population sizes). Frequently they get vegetables and repashy cut from the same piece. Also, the fourth egg bunch I had put in the breeder net before the die off has had ZERO deaths outside a couple poor hatches. I also am skeptical about it being an oxygenation issue since the deaths were not all at one, no one is gasping at the surface, and I have my filter literally pouring water into the tank through the breeder box AND an airstone in a sponge filter.

I am puzzled at what might the problem be since:
  • If it was a water quality issue, why would the fry live but the older babies die?
  • If it was an issue of diet, why would the babies in the 20-gallon be doing fine if they are receiving the same type of food form the same source?
  • If it was a disease, again, why would the fry in the breeder box be fine and survive?
Even if there are no ideas what could be causing the deaths, my other question is what should I do with the breeder box fry? Their yolks are gone or almost gone and I am nervous to dump them into the 10-gallon tank like normal if there is an issue killing the babies, but I am also scared of transferring them to the 20-gallon in case it is something contagious?

Thank you again for reading this and any and all help!

1. Symptoms

There are no visible growths or signs of infection on the fish, such as red streaks or white spots. The only notable changes are that, while the bellies are “dark” and visibly “round” with food like normal, it seems like some of the older (about two months old) pleco babies have a noticeable bulge on their right side. This swelling is not visible in all the babies, especially in the younger ones, and not in all the dead pleco babies. Also, when in the process of dying, they “trash,” swimming rapidly in place or around the tank before seemingly passing out and going limp. They may do this trashing process a few times before dying.

2. Size of tank and other tankmates.

It is a 10-gallon grow out tank, only set up to give the babies get to about 3/4”-1” before moving them back to the 20-gallon tank I use as my primary breeding tank. The only tank mates are ramshorn and pond/tadpole snails that I use to help make sure eggs are kept clean and any excess waste from food or plant melt is broken down efficiently.

3. Water parameters.

a. Ammonia – 0.0ppm
b. Nitrite – 0.0ppm
c. Nitrate – 0.0-10ppm
d. Ph - ~8.0

I have tested multiple times throughout the day, before and after water changes with these results. Before doing more frequent water changes the nitrates were consistently 10, now they are 0.0 and I have very soft water so I add two small “wonder shells” to add minerals to the water.

4. Filtration and water change regime.

a. Filtration – An Aquaclear 20 that pours directly into the breeder box I put the eggs in. The breeder box is made primarily of fine netting in a plastic frame that helps it float, so water can push out of the net, also the intake is outside of the box. There are also two sponge filters in the back corners of the tank, with one currently powered with an airstone inside.
b. Water Changes – Before the deaths: Roughly once a week, most due to the breeder box set up and freshly hatched fry refusing to let go of the netting despite the water sinking. For the last week: Every single day. These water changes were roughly 75% percent, facilitated by me draining the tank 30-50% at least twice, if not three times.
c. Water treatment – Fritz Complete

5. Diet.

Primarily carrots and Repashy food. The repashy mix I use is 2/3 “Morning Wood” and 1/3 “Bottom Scratcher.” The carrots are almost constantly in the water, with me pulling out the old pieces within 48 hours and the new pieces blanched before added to the tank. The repashy I feed every other day and is to provide protein to the growing babies. I have fed Zucchini in the past but stopped in the last couple weeks due to my concerns about it breaking down rapidly in the water. I also have three type of “wood” in the tank for them to rasp on, which is ~4 pieces of small cholla wood (one kept in the breeder box), two pieces of driftwood (looks a lot like Malaysian driftwood, bought at local pet store in fish department), and a coconut hut.

6. Temperature of tank water

Before the deaths, ~77 Fahrenheit, took out the heater to drop it to ~73 Fahrenheit out of concerns that the heater was “malfunctioning” and perhaps leaking contaminates into the water.

7. Treatments Used already

Tried to treat with PraziPro (Anti-parasite med) due to the bulging side and to hopefully correct the amount of detritus worms in the tank. More deaths occurred 2 days after this treatment, so I started doing daily water changes and add Paraguard (Seachem’s gentle “general” cure) after each change. After 4 days of this, still getting deaths.

8. A Pic

I do not really have any good pictures of the dead babies, but I have one (poor) shot of some. (Sorry for the gruesome nature of the image too)
Dead 10g Pleco Babies.JPG

Thank you again for reading this and any and all help!


Scott Roh

New Member
Jan 11, 2021
Did you ever come up with some thoughts, or get beyond this, as I see a year has passed but I've just joined these forums? For me, bushy's were something that I stumbled on to a breeding pair, and had success for a good year (video below) but you have way more moving parts than I did... With the youngins, what I'd do is have a water change on 'the parent tank' that was 50 gallons+ and after a couple days I would run a tube from that water to the tank for the youngins. I'd only transfer 2-4 gallons into a 10 gallon tank where the young ones were.... that way I knew it was water/tank they'd started from and in that 10 gallon I'd have minimal things going on that could play with conditions.