It is not possible to provide a reasonable answer without having a bit more information:
1. What brand of test kit are you using. This matters since we need to know how it is measuring ammonia, Tests which read as you described are usually measuring only the nitrogen ions as opposed to what most hobby kits measure which is total ions.
2. Then we need to know both the pH and the temperature of the tank water. This will allow us to determine how much of the ammonia is in the toxic NH3 form, It is this that we must protect tank inhabitants from.
3. Was your tank fully cycled before your added the new fish or were you trying to do a full blown fish in cycle?
As a general rule of thumb if the NH3 component is .02 ppm or less there is little worry at the total ammonia levels you may be reading. At .05 ppm damage is being one for sure and action must be taken.
Finally, what action one might need to take also depends, to some extent, whether the ammonia is related to cycling where it is expected to go away fairly soon vs in an established tank where we normally expect readings of 0 all the time. One is normal and the other is not.
The next issue is that testable ammonia will usually result in nitrite. So this is another issue that may need to handled. Fortunately this can be done with the addition of some minimal amount of salt which will put chloride into the water and that will block any nitrite from entering the fish.
So, depending on your water pH and temp. combined with how test results show things moving, we can get a good idea of what action may or may not be needed.
If your tank were pH 8.0 and 80F, .75 ppm of total ammonia would have .0465 ppm and be closing in on the red line we don't want to cross. But if your tank is pH 7.5 and 77F, that same .75 ppm would have only .0135 ppm and the fish should be OK in this for some time. So as you can see, there is no universal answer as to what one should do at .75 ppm without knowing the other parameters.
I would suggest you read the sections on Some Important Facts About Ammonia here:
http
/www.fishforums.net/index.php?/topic/433778-rescuing-a-fish-in-cycle-gone-wild-part-il/
If you are trying to do a fish in cycle and added more fish before you were getting 0/0 for ammonia/nitrite, then the above advice would have to modified as things are going to go downhill faster very quickly. And in this case you should also read this
http
/www.fishforums.net/index.php?/topic/433769-rescuing-a-fish-in-cycle-gone-wild-part-i/