This question is always very difficult to answer. Nevertheless, we would like to give it a try. Floor screeds in residential areas are usually designed for a live load of 1.5 KN/m². With an aquarium or other heavy object exerting a pressure of around 153 kg/m², this value would already be exceeded. Therefore, you should first clarify whether the screed construction can withstand the load.
But now to the parquet.
Our answer refers exclusively to parquet firmly bonded to the screed. The decisive value for parquet flooring is the ability to withstand transverse pressure forces. In principle, the value indicates the force from which permanent crushing of the wood starts. However: The values are determined with absolutely flat test specimens, thus ensuring an even distribution of force.
This is certainly not the case with your aquarium. If your aquarium stands on 4 feet, for example, the parquet will certainly get strong impressions. If it stands on a base, the base will probably not lie flat on the parquet, but only with the frame. So here too, the distribution of the weight on the supporting surface must be assessed. If this weight distribution is then clearly below the average transverse compressive strength, there is no danger of indentations on absolutely flat surfaces. Absolutely flat surfaces, however, are not to be expected from either the parquet or the base of the aquarium. The risk of crushing the wood fibre therefore remains high.
An example: The base of an aquarium has the following dimensions: 180cm x 60cm, the frame has a thickness of 1.5cm and lies fully on the parquet. This results in a contact surface of 720cm². If the weight of the aquarium and the base is 1000kg, the pressure per cm² is 1.39 kg/cm². This would prevent the wood from being crushed.
But: As already mentioned, this only applies to absolutely flat surfaces. If the base or wood is slightly uneven and the base is only at three points with maybe 10cm², the pressure at this point increases to 70 kg/cm². This means that the compressive strength of wood is exceeded many times over.
The wood is therefore squeezed until all surfaces bear evenly. The squeezing is not reversible.
This is certainly an unsatisfactory answer for you.
Nevertheless, the answer is simple: you must achieve the greatest possible distribution of force and the parquet does not suffer any damage.
The above example refers to the use of solid oak parquet. However, the example can also be transferred to other woods. The softer the wood, the greater the risk of damage.
You should not use floating multi-layer parquet (finished parquet). In this case, further risks result from the laying method alone.
And also remember to have the load-bearing capacity of the screed confirmed.