Can somebody please tell me what this is???

promise

has anyone ever seen this before?
it is only on the silicone, it is no where else i.e glass, plants, it doesn't seem to be affecting the fish but im still a little bit concerned.
i noticed it last night when i went down to feed the 5 cichlids in the 75 gallon tank, its semi planted with anubius and ferns.

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onefish2fish

its a used saltwater tank, thats the left over from coraline algae. you cant scrape that part off because of the risk of damaging your silicon seal, however your tank should be fine.
welcome to the forum!

promise

its a newly re-sealed tank, would that stuff of come from the glass even after i cleaned the tank thoroughly??
also its a freshwater tank with 5 convict cichlids in it? i didnt think marine algae would survve in a non salted freshwater tank