Generally, the magnets used in aquarium are mostly water pump rotors. If you have a water pump in your water tank, its magnetic field is much stronger than that of a magnet, because the water pump relies on the strong magnetic force generated by the coil to make the rotor rotate at high speed to achieve the purpose of pumping water, and the rotor is a permanent magnet. If you don't believe me, you can remove the rotor and put it on the iron to see if it can attract you.
Karich is a manufacturer of strong magnets. The company mainly produces NdFeB strong magnet blocks, columns, rings, countersunk holes, multipole magnetizing, radial products, magnetic tiles and various triangular, convex and trapezoidal shaped magnetic steels.