Have gotten past the first hurdle. These are 5 day old Darwin Algae Shrimp zoe that have been in salt water for the last 4 days. (sorry - no macro photo gear.. this is actually a phone shot cropped for a little extra magnification).
The problem I had with deaths before seems to be related to the salt mix being too fresh and the salt is apparently caustic. I'm mixing red sea brand marine salt with a fresh greenwater culture. The freshwater algae don't survive long, but the water is a nice olive green and has lots of minute particulates that an air stone keeps suspended so hopefully there is something for the zoe to eat. I did read of one guy raising Amano shrimp in salty water with a freshwater algae culture so who knows.... it might work.
I'm being a bit sloppy with the salinity as I don't have a hydrometer or refractometer yet... I'm just using some electronic scales to weigh out 35g salt per 500ml of water (double seawater concentration) as a stock solution. Then every day I half fill a 125ml bottle with fresh greenwater and top it off with the concentrated seawater which brings it back to ~seawater. I know the salinity is a bit lower as I added some additional freshwater on the day I dropped the zoe in because I was wary of osmotic shock. (hillbilly bucket chemistry )
These are tiny... ~ 1.5-2mm long at a guess
Edit: ~10 days old
Green water cultures are slowly crashing (cooler weather or copepod bloom eating the phtyoplankton!). There is a fair bit of gunge in the bottom of the salt tank and I've stirred it up a few times to re-suspend more "food" into the water column.
another week...
Another week on... little black eye spots visible now.
I'm guessing ~80-90% survival at this point. Still planktonic mostly swimming in vertical position "bum up".
They are positively photo-tactic and the sun is hitting this corner of the tank so when I turn off the air pump to still things down for a photo they congregate here.
Approx 20 days old today. Now seeing a few that appear to have settled as shrimp-like postlarvae even though they are still very small (3-4mm). When shining a bright torch on the side of the tank now there are a few individuals that launch from the bottom and swim forwards like the adult shrimp do (very fast!) away from the light. The planktonic larvae move towards the light.
If anyone in interested here is a nice review paper on the life cycle of freshwater shrimps that have marine larvae from the Latin american journal of aquatic research.
Another week on... so ~ day 24
Have 30 ish that have transformed @ ~ 4mm
Still *plenty* in "float mode" still...(torch shining on this corner)
Its Thursday so we're another week on and approx 1 month old.
After a few days to a week of post-larval shrimplets swimming around in the estuary its time for that big migration up river back to freshwater!
So last night I used a torch to attract all the still planktonic zoea that had not yet transformed and siphoned them off into a coffee jar so they can continue development in "marine" water.
This leaves me with a small tank with a gazillion little shrimp.
The tank is approx 15L at near enough to 35ppt salt (sea water concentration). I'm siphoning off water (through an airstone so the little shrimp don't get sucked out) and replacing ~1.5 L of salty water with fresh water each morning and night.... so in 5 days (ish) the tank should be close to fresh (and the big migration complete).
Last night I used 1L from my greenwater tank because I wanted to make sure food is abundant (as can be seen in the green pic below) - the salt kills most of the algae and it settles and I presume the shrimplets eat it. I can see shrimps trailing poo strings so I know they are eating something. There is a fair amount of accumulated dead algae/diatom/mess in the bottom of the tank also.
When the freshwater goes into the tank there is a flurry of swimming which I'm equating to the instinctive upstream migration response. I couldn't get clear photos as they herb around very fast.
I *think* the mortality in this transformation stage might be a bit higher - hard to tell as there are so many. I'm just not certain there are as many swimming around today as there was 3 days ago (despite more larvae joining the transformed masses). Certainly once transformed to eat benthic food there is a big jump in growth rates. This time around I wanted to cut my losses and get them into freshwater in case there is a time limit. ie if you dont get to freshwater within a certain time they might die. I dont know. Hopefully they can grow on in salt water for a long time - in which case I could leave them and just wait until all the planktonic zoea had transformed (e.g. another 2 weeks perhaps) and then migrate the whole batch into fresh water.
[QUOTE=Grubs;498234] So last night I used a torch to attract all the still planktonic zoea that had not yet transformed and siphoned them off into a coffee jar so they can continue development in "marine" water.
[/QUOTE]That was a little over 2 weeks ago when I put the first batch of juveniles into fresh water. This second group of "late bloomers" from the coffee jar made it through. Pic below in a small single serve yogurt container.
On quick count thats another ~100 "juvies" joining the mob. The size variation (3-8mm?) is because the biggest transformed to juveniles ~2 weeks ago and have been benthic feeding on the crud in the coffee jar while tiny ones did laps in the water column as plankton until just a few days ago.
The biggest of the first lot are approaching 15mm.
Rough guess ~300-400 juveniles from 2-3 berried females.
Second Generation
DAS breeding has been a little too successful and I'm now rearing a bunch of juveniles. Planning to have ~100 or more in my display tank but it will take a good 12 months to get them big enough so the fish don't clean them up. Now concentrating on C. typus which are proving to be significantly more challenging (and frustrating) where all drop dead in the same water that is successful at rearing DAS.
