Posting this unofficial report just of the sake of sharing about my first ever attempt to breed some egg layers. I didn't know about PVAS at the time and wasn't keeping any notes.
I tried my own way of doing things that would replicate warm and stagnant conditions followed by a cool rain. I've never believed a water change is necessary, only a temperature and flow change. I personally think the triggers and water parameters are over-thought, at least for captive-bred fish that don't know any different. I've never had the opportunity to experiment with wild-caught fish.
Name:Travis
Scientific Name of Fish: Corydoras aeneus
Hobby Name of Fish: Bronze cory
Method of Reproduction: Egg layer
Number and Gender Distribution of Parents: 1 pair
Origin of Parents: Mother from a PetCo probably five years ago, maybe even older than that. Father from a PetCo early 2023.
Approximate number of eggs: 150+ probably
Date of Hatch: Mid-August 2023
Date of Free Swimming If Hatched: Noticed them about a week after the eggs were laid.
Approx. Number of Fry at 30 Days: More than 100
Approx. Number of Fry at 60 Days: More than 100
Aquarium Conditions:
Primary tank: 55 gallon community tank, plastic plants, black and green gravel, some wood , granite and quart rocks
Spawning tank: 30? gallon bow front. Black and white pea gravel, piece of unknown type wood, some Smartweed from my yard that survives in water for quite a while-some had degraded. The tank also had 4 or 5 blue neocaridina shrimp in it and a few local stream caught ramshorn type snails.
pH - 7.2-7.4
General Hardness (ppm) - 90 maybe?
Average Temperature (F) - 75 degrees
Average Nitrate (ppm) - 0
Water Source: Loudoun tap + rain water
Water Changes: Pretty much never. 55 probably gets about a 25% change once a year with the substrate completely stirred up.
Filtration System: Whisper Power Filter only in the 55. Sponge and Whisper Power Filter in the breeding tank.
Additives: none
Lighting Type and Timing: Basic aquarium hoods with fluoroescent tubes. 55 is lit for about 10 hours.
Food Fed to Parents and How Often: Normally flakes, started feeding frozen blood worms once moved to breeding tank.
Food Fed to Fry and How Often: Initially fed on stuff accumulated in the gravel or on the wood + crushed flakes a few times per day
Spawning process: Moved pair to spawning tank. Turned off power filter, kept sponge on. Increased temperature to 80F for a few days. Fed them bloodworms for those few days. Left the light off. After those few days I turned off the heater and turned on the power filter. Within a couple days there were probably at least 15 eggs laid on the glass on the front left side. By that time it had cooled to 72F. The power filter is on the back left side and the sponge is at the bottom of the back left. I returned the parents to the 55. I turned on the heater again to get it back up to about 80. Both filter remained on to maintain flow over the eggs. After a few days nothing had hatched so I wasn't sure if they had fertilized. One had started to get fungus. I didn't pay any attention to them for a few more days. The next time I checked they were all gone. I thought maybe snails got to them but then I noticed loads of fry at the bottom in the gravel. At that point I turned off the power filter so they wouldn't getting sucked up.
It seemed like some fry may have had issues getting stuck in the gravel. After about a week I removed 20-30 and put them in a small plastic tub just in case. But I didn't maintain that very well and they all died. After about a month and a half most had been growing really well. I moved all the runts to a new 10 gallon hoping they would get more food. Occasionally one would die. The ones dying seemed to maybe have not properly developed properly from the get-go. Besides not growing at the same rate, the tails have a paddle type shape or pinched appearance rather than fanned out. In mid October I moved all into the 55 which had now been changed with all the previous occupants moved to the 125. It had a few pairs of guppies which had been popping out a few fry every few weeks until recently when more than 40 new ones appeared. Since moving them I still occasionally find one of the runts dead. But the others continue to develop really well and are very active.
The 55 full of baby corys and guppies
Comparison of runt to an average one about 1" long.
Some runts, notice the tails
