There are a few methods to strengthen the table though I can't guarantee 100%.
You may need to observe/monitor the table's condition especially the middle part from time to time.
1)Put a thick wood (I think plywood is ok) under the aquarium to spread out the weight and to prevent the middle part from sinking.
The thicker the wood the better it is. Even putting a few pieces of wood are ok.
Also, add a piece of styrofoam or rubber mat directly below the aquarium. You must ensure that the aquarium is sitting on an even surface to prevent stress on the aquarium glass.
Also, cover the table with a piece of plastic cover as wood may get warped when in contact with water.
2)You may need to reinforce the middle part by removing a few drawers and replace them with some woods.
Or if there is still space in the middle, you can squeeze in some woods next to the middle support to strengthen the middle part and prevent it from sinking/sagging.
3)Just double check the quality of the metal joints and overall structures.
Make sure they are strong and can withstand heavy duty. Big srews are usually strong.
Are they built for heavy weight or light weight storage?
Note: You might be able to find some woods from Ikea though they are mostly made of chipboards to cover the top of your table.
I think they are ok if they are thick enough or very thick.