Unless you know the specific gravity, etc etc - My recommendations were based on the fact that you said your tank was at 50% capacity (I assume water-wise) - which means your salinity is double normal. Not to mention all of the dissolved organics. Though its possible that your tank is still cycled - there is also a chance - again depending on your salinity, that it is not. And - when you all of the sudden add new water with 1/2 the salinity, some of the bacteria that are there are not going to survive due to lysis. In any case - part of this depends on what you meant by 'the water level was 50 %'' - if it was evaporation - thats an issue potentially - if it was because you removed 50% and left it there - thats less of an issue. Otherwise I agree with
@brandon429