Instructions
Pick a sucker fish that is larger than your turtle. Your turtle probably will grow faster than your fish, especially if the turtle is young. You need a fish that remains larger than the turtle. The sucker fish known as Plecostomus grow large and have an armor type skin and scales to protect them. Ask the salesperson at the pet store to recommend a fish that can live comfortably in your tank.
Float the bag in the tank for several minutes with the fish still inside. This will help the fish adjust to the new water temperature, and it will allow you to watch the interaction between your turtle and the sucker fish.
Free the fish from the bag if your turtle doesn't bother with it. Continue to monitor the interaction between the two until it becomes obvious that they can live together. Remove the fish from the tank and if your turtle tries to nip at it or tugs at the bag.
How to Put a Sucker Fish in a Tank With a Turtle
Turtles are notorious fish eaters. They often are indiscriminate on what fish they will snack on. That can be a problem if you want to employ a sucker fish to reduce algae levels. You can do it however, if you just take some measures before introducing the two to each other.