It can be caused by the ceramic ring but rare though I had one encounter. If he is unsure, get the proven Sera ceramic ring.
If he had not started planting, I suggest that he don't and fill the tank with water to full and soak the base fert for 1 week. Change the water on the 4th and 7th day, 50% each time, no light should be introduce during this period. Filter should run at all time.
This will give the setup and the plant a better start as the risk of running into nutrients peak from the new base fert is greatly reduced.
Have fun.
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