Accidentally brushed my teeth with a toothbrush i used to scrub out a dirty fish tank. now have a hacking, wet cough and sore throat. is this caused by the fish tank, or a cold/covid?

Your symptoms almost certainly have nothing to do with the fish tank or toothbrush. You are right to be concerned about a cold or COVID, especially if you have not yet been vaccinated. Get tested for COVID as soon as possible. Good luck!

Make sure you do not have high body temperature , body ache .If symptoms increase in three to five days ,see your primary Doctor for proper diagnosis and treatment.