unitary injection molded clear plastic containers the material preferably is a high temperature polycarbonate if autoclaving will be used as a part of the tank maintenance procedure an outwardly projecting flange 68 is formed around the peripheral edge of the open top end of each aquarium tank 6 fig4 8 flange 68 forms a shoulder 69 that also substantially surrounds open top end of aquarium tank 6 one of end walls 62 includes a u shaped opening 70 that separates flange 68 and shoulder 69 at the top portion of that end wall 62 the inner edges of u shaped opening 70 form an inwardly projecting flange that further defines opening 70 the bottom 64 of the tank comprises inner side surfaces that slope inwardly and downwardly preferably at a sharper angle adjacent that bottom than higher in the tank the inwardly sloping bottom panels intersect one another to form an elongated trough or sump channel 76 extending the length of the tank sump channel 76 defines the lowest portion of aquarium tank 6 and in the embodiment shown is positioned centrally along bottom 64 sump channel 76 also extends parallel to the top edge and flange 68 in the embodiment shown such that channel 76 has a downward gradient to a point only when the tank is tilted such as when supported in the rack the sump channel 76 can be placed along one side or the other instead of centrally or can be diagonal or otherwise formed and sump channel 76 can be inclined relative to the flange each of these structures may be arranged to provide a bottom inside contour that defines a gradient leading from all points on the bottom to a predetermined point from which sediment can be collected by appropriately locating the drain inlet.