Rotifer Culture Crash! Help!

[ml708]

I started a rotifer culture in 4l of seawater 3 days ago and fed them PhytoGreen-M daily. I conducted a 20% water change daily as well. The culture tank is well aerated by an air pump.

Today I noticed that the water was clear yellow instead of a murky suspension of rotifers. I noticed a thin brown layer at the bottom of the tank and presume them to be dead rotifers. Upon shining a torch into the tank I noticed some live rotifer specks but they were much fewer than before.

I'm quite worried!

 

[tektite]

How often during the day is the water yellow? That typically means the rots are out of food. Why the large daily waterchanges? How much air do you use for aeration?

 

[ml708]

It is yellow because of the phytogreen I put in, and I noticed that the water becomes transparent when they have eaten up the food. I do the water changes to keep ammonia down and I just use a typical aquarium airstone for aeration.

The seller now tells me that he kept then at sg of 1.016-1.018 and I didn't know that, so I was keeping them close to 1.025 which is the sg of my main tank. Not sure if there was any osmotic shock.

I stirred up the brown layer and it seems that the specks of rotifers are back. However I don't know if that means that all is well. Do they form a layer sometimes? If they do why does that happen?

 

[tektite]

Couple things, waterchanges like that will keep the culture pretty thin unless you filter the rotifers from the water that was removed and return them to the culture, its better to control ammonia with something like cloram-x. Don't let all the food for the rotifers run out. Rotifers need to eat constantly, if they get a period of no food it will shock them/throw them off, delay reproduction. If the dead rotifers all settled to the bottom of the tank, you probably don't have enough water circulation. Don't use an airstone, just an airline from the pump. Try for 2-3 bubbles per second. It should be enough circulation to keep everything in suspension. If the rotifers can congregate in one location, there's not enough circulation. Reproduction could have been delayed from osmotic shock, if that's the problem just wait it out, their numbers will begin growing again soon. I raise my rotifers at 1.025 as my tanks are all at that salinity, its a good idea to raise the rotifers at the salinity of the tank they'll be fed in, so there's no osmotic shock when fed.

 

[ml708]

I discovered the reason why my water was always yellow and never green. I switched to using phytofeast to feed the rotifers and now have greenish water. Phytogreen did not have the same effect, probably because it has fewer algae species. I will report back on how things go from here.

 

[ml708]

Culture appears to be clearer now, but I'm not sure if that means that the rotifers are eating, or if something else is eating the algae or if its just plainly decomposing.