Brine Shrimp Dying In First Hour

[UTJeeper]

I have been successfully hatching Aquarium Co-op green tin brine shrimp in a Ziss hatchery for months to use as food for my Apisto fry. Things had been going fine for months and then all the sudden about 2 weeks ago my hatches starting dying and sinking to the bottom of the Ziss hatchery. I am still getting a good hatch rate, they just die within an hour of hatching some almost immediately.

• I tried scrubbing the Ziss hatchery real well, both with just fresh water and also with dish soap and a thorough rinse.
• I fill water to the same level, about 1 inch from the top.
• I have kept the salt constant with 2Tbsp of instant ocean that I've been using all along. I let it dissolve for 1 hour before adding eggs.
• I have kept the temp constant with the aqueon 5w mini heater at about 29C, I observe the temp several times a day.
• I tried RO water to eliminate a change in water quality from the tap as an issue, no help.
• I tried different air volume, less aggressive, more aggressive, no help.
• I even tried a different brand egg, BNYEE eggs hatched and died too.

Any ideas on what would cause this to happen? Until 2 weeks ago I was getting nice healthy hatches for months. Thanks for the help!

[Guppysnail]

Could something like an aerosol being sprayed have contaminated the salt?  Is it a new batch of salt that may be contaminated?

[UTJeeper]

Aerosol probably not, but I did just break into a new bag of the sea salt around that time. It is the same brand I have been using but did not think about the salt possibly being bad. I guess I'll try a batch with different salt to eliminate that as the issue. Thanks for the idea.

[UTJeeper]

Update, so I added a second Ziss hatchery with the goal of changing the process. So I filled Ziss #1 with RO water and 2 Tblsp of Instant Ocean. I then let it sit overnight and add eggs after I get home from work in the PM. When I add eggs to #1 I then setup #2 with RO water and salt and let it sit overnight. So each day I am harvesting from one hatchery and reset it while I am adding eggs to the other. For some reason this has worked to keep my hatches alive.

For whatever reason I needed to let the temp and salinity settle in for a long period of time before I add eggs. That cycle time required two hatcheries so that I have a hatch every day. Anyway, I thought I would document what worked so that any other newb in the future might learn from my trial and error.