Combined symbology(unique values and Graduated value?)

[ReaCamileMaglaya]

Hello to all of you.

I'm having trouble illustrating the water ecosystem using a variety of colours while maintaining the feature where the circle size indicates the ecosystem's concentration at a different range. I can use "vary symbology by attribute" to adjust the circle's size, but it only gives me four values. Is there a method for me to display the aquatic ecosystem in colour while varying the circle sizes in a range that corresponds to what graduated symbology will produce? Will this one work with arcade symbology?

I will be truly grateful for all of your responses. Thank you.

[AdeolaEmmanuel]

This is on ArcGIS Online I suppose? Couldn't you manually set the range to your preferred scale and use "Add attribute" to vary the individual points by the color of interest? If I'm getting you right?