Measuring Rotifers

[roczero]

Hey all. What is the best procedure to properly measure out rotis to feed fry? How much straining, etc? How do you really know how much you have? What is a proper amount to feed per day?

[Luis A M]

You aim to have 1-2 or more rots/ml in your larval tank.Take a 2ml sample with a pipette and check with a scope or a loupe.You must see at least 2 rots.Otherwise,add more.
For a rough estimate,just shine a flashlight from above.

[roczero]

Thank you. So for the most part you guys are just eye balling it in the laval tank?

[roczero]

I just measured 2 ml sample of larval tank water from the middle of the tank and put on a piece of glass. This is just a small amount of water. I used a flashlight underneath, and I can see dozens of rotifers. Maybe 100. You said I should see 1-2. Is it a problem that I have 100x more rotis in my tank?

[Amie]

If you really want to know the exact number of rotifers you have, I would recommend purchasing a hemocytometer. These were designed for the medical field, in order to count blood cells. Here is a link that gives directions on how to use a hemocytometer for counting cells ... you would use the same method for counting rotifers. Using a Counting Chamber. And here is an online hemocytometer calculator that is helpful. hemocytometer calculator.

Luis' statement, that you need at least 2 rotifers per ml, means just that ... at least 2 rotifers per ml. Having one hundred rotifers in a single ml is very possible. The more you have, the more attention you need to pay to feeding them and making sure they do not crash the fry tank.

(I am sure you know this, but just to clarify, 1 ml of water is equivalent to a single drop of water.)

[roczero]

1 ml of water is equivalent to single drop of water? Is that how you are interpreting it? 1 ml equals 1 cc. A cubic centimeter is much more than a single drop of water. 1 ml or cc is a full insulin syringe. I would guess that a ml of water is more like 20 drops of water.

Luis said to measure 2 ml of water and count the number of rotifers. That would be more or less 40 drops of water. Is this not right?

[Amie]

You are absolutely correct, and I completely messed that up. 20 drops is equivalent to 1 ml. Sorry about that. The rest of comment still holds. It is not uncommon to find over 100 rotifers in a 1 ml, or 2 ml, amount of water. However, the more rotifers you add to the fry tank, the more important it is that you feed them with phyto and watch carefully that they do not crash the system. There is nothing wrong with raising them in the tank with the fry, many breeder do. Just make sure the rotiferes have food so the fry continue to eat gutt-loaded rotifers.

Hope I didn't confuse things.
Amie