Edexcel exam board Algal Balls

I started my second attempt at culturing algae a couple of weeks ago but I've hit a problem. The first two weeks it was going really well and the solution was starting to become a darker green but this week it seems to have just started separating and sticking to the sides. Over the weekend it had completely separated (like it was just clear liquid with algae just sitting at the bottom of the flask). I've shaken it and turned the air pump up to max but it seems to still be settling/sticking to the sides. I'm not sure what I've done wrong :(
You do get that - just keep trying to break it up - I use the aerator by moving the stone (on full bubbling) across the sides to dislodge - it should recover if you regularly keep doing this
 
I started my second attempt at culturing algae a couple of weeks ago but I've hit a problem. The first two weeks it was going really well and the solution was starting to become a darker green but this week it seems to have just started separating and sticking to the sides. Over the weekend it had completely separated (like it was just clear liquid with algae just sitting at the bottom of the flask). I've shaken it and turned the air pump up to max but it seems to still be settling/sticking to the sides. I'm not sure what I've done wrong :(
This happened to me, the way I fixed it was by replacing the air stone (although you could try cleaning it)
 
This happened to me, the way I fixed it was by replacing the air stone (although you could try cleaning it)
Good call - it is common for this to happen or even not have a powerful enough pump - the bigger and deeper the vessel the stronger the pump required. With 5L demijohn, I use a Tetra APS 400
 
Good call - it is common for this to happen or even not have a powerful enough pump - the bigger and deeper the vessel the stronger the pump required. With 5L demijohn, I use a Tetra APS 400
I'll try cleaning the air stone because it does seem to be worse in one of the flasks. I do have the same pump as you and the volume of my culture is around 1.5L at the moment (split across two conical flasks). The first time I tried to culture I put the 30ml starter straight into 5L but it just never seemed to go any greener so this time I've put the starter into a smaller volume to try and make myself 200ml of concentrate that I can then put into 5L like you said you do when sub-culturing.
 
Do you think we need to put more water in the flask? The tech followed the instruction sheet, but everyone here seems to have about 5 litres instead of the small amount we have set up
 
Do you think we need to put more water in the flask? The tech followed the instruction sheet, but everyone here seems to have about 5 litres instead of the small amount we have set up
Yes, you need a much larger volume because you have to concentrate the culture up 5l demijohn
1678697805533.jpeg after about 2-3 weeks1678697754015.jpeg

Let it settle for a day or so
1678697887029.jpeg
discard the clear top solution then make balls from bottom dark green 'algal soup'
1678698005329.jpeg
 
I have a 500ml RB Flask, and keep it topped up.

Also once it is growing put a subculture sample in the fridge incase it crashes and you have to start over.
 
@Peter Sigsworth the algae that you sent me last year went nice and opaque, but never went deep green - apart from the first couple of weeks when it was quite bright green it's always been shades of yellow-green. A couple of times when it started to look decidedly unwell I tipped out all but about 2 inches depth and topped back up with distilled water and a couple of drops of baby bio, but the same thing just happens again :confused: I put a lamp on it about a fortnight ago, which doesn't seem to be making any difference so far. Any other tips ?!
 
How about me waiting until I get a nice large quantity of algae and I'll post a 7ml vial of the concentrated stock culture to you - try to subculture that. I know my stock works well - PM me your school addresses first two gets them and if you can get a result then we know that my strain is the one to go for (whatever it is)

Hi @Peter Sigsworth, those this offer still stand? Our Algae that has been growing like a trooper for years is suddenly starting to die on us.
 
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Hi all - today is the day I am going to trial the Algal balls practical. I have a lovely "pea soup green" culture of algae. What's the best way to keep back a subculture for next academic year? We bought a starter culture last year and didn't end up trialling it so it sat on the shelf over the summer hols and survived until I started the culture about 6 weeks ago. I have looked at them under the microscope and seem to have a pure culture of the Scenedesmus quadricauda so keen to save some back and save us having to purchase again.
 
Just keep back say 100ml of your culture empty the rest into another container to make the beads add the 100ml back into the culture vessel and top up with 'safe' water/fert and aerate for your next batch. I kept a batch on the go at all times.
 
How long can the algal balls be stored for? Thinking we would really have to make them up for our double science students and wondering if they could be stored for a two week period perhaps?
 
How long can the algal balls be stored for? Thinking we would really have to make them up for our double science students and wondering if they could be stored for a two week period perhaps?
several weeks in the fridge - you can also re-use just rinse in a sieve and then keep in water.
Just 'wake them up' on the window ledge in the sun prior to use
 
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