If rinsed and cleaned correctly could I collect substrate from a local lake for my aquarium? It appears to be a mixture of sand, pea gravel and what looks to be a little mud but it settles very quickly. Would this be safe, for arowanas?
Rinse and throw some clorox in it, let it sit awhile, to make sure you kill everything. Rinse again a few times and throw some dechlorinator in.
That is what I would do. I don't see the harm in using the substrate. For an arowana I don't seem\ him ever even going down that low to worry about it.