I purchased a used 36 gallon bow front. I have it completely filled with water since this past Sunday and it's been dry. I'm concerned with these bottom seams .the caulk seems discolored ,brown. should I be concerned? i can't tell if it's mold or just dirt on the seams from the previous owners set up . I don't really feel like getting into a recaulking job with it .if that was the case I probably would just buy a brand new aquarium.