Skip the filter.... Load with less fish.
I think you should consider a sump/refugium instead of a filter. Consider the ability that this will provide to the lesson.
When you have a sump/refugium you will be more able to show and teach the various biological lessons, much better, to kids. They can watch the cheato growing. A natural filter. You can explain how the growing refugium algae is using the nitrate to build its structure and how that cycle reduces the level of nitrate.
How can you easily rationalize a mechanical filter to the natural system?
A sump/refugium could even reduce operating costs by stretching water change times a bit.
I think you should consider a sump/refugium instead of a filter. Consider the ability that this will provide to the lesson.
When you have a sump/refugium you will be more able to show and teach the various biological lessons, much better, to kids. They can watch the cheato growing. A natural filter. You can explain how the growing refugium algae is using the nitrate to build its structure and how that cycle reduces the level of nitrate.
How can you easily rationalize a mechanical filter to the natural system?
A sump/refugium could even reduce operating costs by stretching water change times a bit.