While Guar Gum can act as a flocculant for dyes, its lack of charge makes it ineffective as a flocculant for most freshwater microalgae. It appears to only be viable if it is modified adding a cationic moeity in its backbone.

Aditionally filamentous fungi effect on flocculation may vary in its effect depending on the microalgae. There are more examples of this fungi in the literature but most are from the Aspergillus genus.

Overall they seem to be food grade but from my own research the direct effects on humans havent been tested for most of them.

Some aditional bioflocculants you could add are:

Cationic polyssacharydes such as cationic starch (http://dx.doi.org/10.1016/j.algal.2014.07.002), guar gum (http://dx.doi.org/10.1016/j.carbpol.2012.09.022) and alginate (https://doi.org/10.1016/j.jpcs.2020.109408).

Yeasts https://doi.org/10.1016/j.biortech.2021.125670

Extracellular matrixes of filamentous fungi, although about it being food grade it depends on the variety, but this refers to the extracted matrix without viable cells.

Fish bones https://doi.org/10.1016/j.jwpe.2022.102808

I will try to add some more if I come across some more. I hope some of this is of use for you.