How do I stop the terracotta balls from rising and falling with each ebb and flow?

Hi All,
I apologize in advance if this was not the appropriate way to ask this question.
I am a high school teacher, using aquaponics to teach environmental science.
We are using an ebb and flow system and we are having an issue with the grow bed.
When the pump fills up the grow bed with water from the fish tank, the terracotta balls rise and float slightly and then they fall again when the bell siphon is triggered. This movement in the grow media is causing the root system of the plants to be disrupted and become unstable and we are finding they are falling over. What are we doing wrong? and how can we fix or prevent this from happening.
Thank you all,

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you can either add more terra cotta balls or lower your water level / standpipe height.

It just takes some days for the balls to sink and stabilize. You can use heavy media to prevent it, such as lava rock, gravel, etc. If you prefer expanded clay, there is one kind of sinking hydroton designed for hydroponics available in my area. It is blackish and heavier than regular hydroton. You may be able to find it in your local hydroponics supplies shop.

In a 12 inch deep media bed the water level should be about 8" (to the top of the stand pipe), the media should be about 10" deep, leaving about a 2" dry zone. Hydroton balls will become saturated eventually. The top 2" typically does not move up and down.

Thank you all for the advice!

Hello Jessie.

Murray Hallam has a saying about the terra cotta balls, they are for people living in posh neighbourhoods with porches with no tow bars.

They don’t work in the real world

To solve your problem of rising and lowering terra cotta balls, replace them with 20mm normal gravel that don’t have the floaty issue. They are also 1/4 or less of the price

This will get less over time when the expanded clay beads soak through and loose their inner air bubbles. Might take a while.
In the meantime as other suggested, lower the upper limit of the water volume so that there is enough clay on top, pushing down.

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Thank you all for the advice. We used some lava rocks as a top layer but even they were a bit to light so we just used a small layer of course gravel. We also played around with the height of the grow bed media vs. the max height of the bell siphons and we found a happy medium. The students had a great time problems solving. Thank you all!

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