do phyto cultures become exhausted?

[salty joe]

I've been culturing Tetrasalmis and Nanno for a little over a year. I keep four 2 liter bottles of each and harvest a liter/day on an 8 day schedule. All went well until recently the tetra started crashing-I'd get another going instead of dosing my tank when a bottle crashed. All four bottles of the tetra crashed.

I wonder, does splitting the same culture of phyto over and over eventually weaken it?

 

[lapin]

I would not think so. Most crashes I have had were contamination problems.

 

[salty joe]

When mine crash, everything drops to the bottom and they get clear. I'm not saying it's not contaminated, but how could I know? BTW, there's no odor. Also, I use chlorine strips to make sure the chlorine I put in my RO/DI water has been neutralized.

Also lately, the Tetra became unstable, whereas the Nanno is OK. At first, the Tetra seemed to grow faster than the Nanno but I didn't have a sechi stick back then so guessing. But I'm pretty sure it did.