What am I doing wrong?

[Zante]

I have a phyto culture that is going real well.
4 bottles, 3 litres each. each bottle has a different strain.

I split it weekly and it is going, as I said, real well.

My usage of phyto has recently gone up because I added a rotifer culture and because I trade left-over phyto with the reef club members, so I decided to take some of the phyto from the split (already mixed) and reculture it once in 4 bottles, 2 litres each.

I know that if phyto is cultured mixed eventually the dominant strain will take over, but in this case I am reculturing the mix only once, and every time I use a fresh mix from the separate cultures.

It has been going well for three or four times, but now every time the reculture bottles just crash. I haven't had a single bottle of recultured mix in four weeks. I do see them getting darker for a short while, then, one after the other they just crash.
The other cultures, the separate ones, are doing just fine.

What am I doing wrong?

Now, here are some details:
all of the water I use is sterilised with sodium hypocloride 15% solution 1ml per litre and neutralised with a solution of sodium thiosulfate (25g in 500ml of water) 3ml per litre.
The air going into the bottles is filtered by going through an airstone and bubbling in 4 inches of water.

The main cultures are near the window, but not on the windowsill and they are lit by 4 x T5 tubes put horizontally. It is basically a 2ft aquarium fixture propped up.

The recultures are on the windowsill and lit by the sun only. They are also close to a window that is always cracked open.

On all eight bottles the caps are airtight and so are the holes for the air to come into the bottle. The hole for the exit of the air is small (diameter of an airline) so there is a pressure of air going out keeping pollutants or contaminants from falling in

In all cultures I use F/2 but I use a double dose in the main cultures and the recommended dose for the recultures.

If you need any other details please do ask.

[Jclaas]

How are your cultures going at the moment?

all of the water I use is sterilised with sodium hypocloride 15% solution 1ml per litre and neutralised with a solution of sodium thiosulfate (25g in 500ml of water) 3ml per litre.

Where did you find your sterilizing method from ?

The recultures are on the windowsill and lit by the sun only.

Can you put them under T5 lights?

[Amie]

Have you looked under a microscope at the crashed reculture?

You mentioned rotifer cultures. Did your cultures start to crash after you started raising rotifers? It is nearly impossible to raise rotifers and phyto in the same room. I would check to see if your reculture has rotifers in it.