Anoxia is no bueno

My main goal today was to flush out any anoxic water from the heated line. When I got to the hatchery, I started draining the header tank and opened the heated line to flush any water out. I let this run while I prepared tripours for tomorrow’s screening and fed Joth’s scallops. After 30 minutes, I shut the heated line off and replaced the 1 micron filter. I noticed that the filter casing didn’t have the black rubber ring around it anymore, but water wasn’t leaking from it. I rinsed the casing and put a new filter in, then turned the heated line back on. I let the line run for 2 minutes while I took a freshwater hose and cleaned the inside of the header tank. After a few more minutes of letting the tank drain, I closed the bottom valve and started filling it.

While the tank was filling, I fed my larvae. I noticed that the buckes were relatively clear, and most of the algae had settled to the bottom.

Figure 1. Tank color upon arrival.

I figured I would increase the algal density to about 65,000 cells per mL and check the color of the buckets tomorrow morning before screening. I don’t want the larvae to go without food dispersed throughout the water for more than an hour, so maybe increasing the amount of food will help maintain the algae level I want. It’s also possible they’ve started to eat more as they’re growing.

After feeding my larvae, the header tank was about halfway filled. I plugged all three heaters back in, kept the heated line open so the tank could finish filling, and rushed out the door to catch the 11 a.m. ferry back. In my haste, there were a few small screening preparation tasks I forgot to do, so they’re at the top of my list tomorrow!

For tomorrow:

• Record which buckets are in which totes (I need this before I rerandomize my buckets!!)
• Turn off cold water input
• Label tubes for larval samples
• Measure out amount to feed ahead of screening, so larvae can be fed while being restocked
• Screen larvae on 80 and 60 micron screens
• Count larvae and drop stocking density to approximately 2 larvae/mL
  • Based on my current count data, Buckets 3, 9, 10 and 11 are the four that are above this stocking density
• Drain heating header and unplug heaters
• Clean and/or replace filters
• Return Rick’s silver heater