If you have spawns growing out you need a continuous supply of baby brine shrimp. If you search the net there are various ways to hatch and harvest baby brine shrimp. What you will find is the big needs for shrimp are warm water and light. For me, to satisfy those needs I have come up with a simple setup that produces plenty of harvestable shrimp about every 24 hours.
Creating a shrimp hatchery is very simple and inexpensive. I use an empty 2 liter Pepsi bottle that I have cut the bottom off. I did the cut about 3” up from the bottom of the bottle so the top could be inverted into the bottom and remain fairly stable. I then placed them into a box that is slightly taller than the Pepsi bottle. I had a bunch of bubble wrap lying around and I put it into the box around the bottle. I did this to stabilize the bottle as well as to insulate and keep the contents warm. The top half of the soda bottle gets water added till about 1” shy of the top. I add 25 grams of salt or about 1 tbs. and a measure of bbs eggs, about 1/8 tsp. I use regular table salt and have used both iodized and non iodized with the same results. If your water is really soft a pinch of baking soda will improve your hatch rate.
The eggs now need to be kept moving until they hatch. Initially I tried to use just airline hose for aerating my shrimp but found I could not keep it down in the neck of the bottle and my eggs piled up there and reduced my hatch rate. So I got some stiff tubing they use for under gravel filters and cut a piece so it could sit in the neck against the cap at the bottom and be a few inches taller than the bottle. I then attached the air line tubing to that and it worked better at keeping the contents moving around. I use a small pump that I put on some bubble wrap to reduce vibration and noise. Over the top of the box I have a light I got from Wal-Mart. I paid about $7 for it and removed the clamp it comes with inverted the light over the top of the box. The light provides both light and heat needed for the shrimp to hatch.
In about 24-36 hours you can harvest your shrimp. They time they take to hatch depends on the how warm they are. For me, the next day about the same time produces a good harvest. I remove the bottle and set it into a 2 cup measuring cup on my counter. I also remove the stiff tubing from the air line hose and run water through the piece of tube to remove salt and calcium deposits. These deposits can quickly build up and make air passage impossible. If the deposits are stubborn, a soak in vinegar or bleach water will get them dissolved.
After a few minutes of sitting you should see a clump of orange in the neck of the bottle and the egg-shell floating on the surface. I have another piece of airline tubing I attach to another stiff tube. I put the tube down into the neck where the orange is but not all the way to the bottom as eggs will be down there. I start a siphon and run the shrimp into a very fine brine shrimp net. You will have to do some searching to get a real fine net. I bought 2 and can not seem to find them again. After they are drained thru the net a quick rinse and invert the net into some water. I have small condiment cups I got from Wal–Mart that I put the water in and then rinse the shrimp into. I then take a plastic dropper and suck the shrimp up to feed.
When you set the shrimp back up you will need to thoroughly clean the container out. If you don’t you will find your hatch rate is affected in no time at all. I have a small spray bottle that I have a weak bleach solution mixed in and spray the Pepsi bottle, scrub with a sponge just for that and then rinse good. Then you can set it all up to have another hatch again the next.