The malicious act is being investigated by police in the town, who believe the incident happened sometime on Saturday evening.
Police say the attack in Ashton Drive caused what is estimated to be in the region of £5000 worth of damage, including apparent vandalism to a TV and a phone.
PC Lyndsey Nicolson of Dumfries Police revealed that the fish tanks may have been contaminated with washing up liquid.
She said: “This is an awful case of wanton vandalism which has sadly cost the lives of a number of tropical fish.
“We want to hear from anyone who may have seen or heard anything suspicious in the Ashton Drive area of Dumfries on Saturday evening.”
Anyone with information is asked to contact Polcie Scotland on the non-emergency 101 line.