First of all, make sure that your SmartTerra is placed on a rigid and level surface. Be careful when moving the unit when there is water inside the reservoir as it may spill out.
There are two locations that are particularly sensitive to leaking. Please make sure that these two parts are secure. Please be gentle when handling the unit to avoid jamming these two parts.
 Water Window |  Drain Plug |
If you see that either of the parts have dislocated, you will have to glue them back on. First, disassemble the unit. Then, wait for the area to dry out, and reattach the part with aquarium glue. Please wait for the glue to dry completely before adding water back to the reservoir.
If it is leaking elsewhere, disassemble the unit and see if there are any cracks or holes. Aquarium glue can be used to fix most leaks.