What is the effect of Saturn in the 3rd house on having an Aquarius sign?

Saturn is ruling your 1st house and 12th house and it is significator of 6th, 8th, 10th, 11th and 12th house. Normally Saturn does well in 3rd house as natal birth chart placement.

You may have sincere and committed relationship with your siblings with limited communication skills as Saturn is lame planet which has very slow speed so person may become lazy, slow and less communicable to the others. As because 3rd house depicts energy, vitality, efforts, health, short distance travelling, mass communication, shoulder etc so person would be slow or lazy in all above activities. He tends to avoid mass communication, you may feel him or her with less energy, valor and vitality. But person would be very sincere and committed to his or her siblings.

Moreover, being ascendant Saturn needs your efforts and energy to make the things in favour. Means one has to perform karma to achieve what he or she is destined for.

Saturn aspects 5th, 9th and 12th house. So it will create hindrance and delay marriage with delayed progeny. Person will have less travelling and settled life but it may take the person away from native and has to spend lots of years in isolation, loneliness, and separation. But this Saturn will bestow good wealth and health.