For the longest time my pair of Kribs were acting like a happy couple. Hiding in caves together and digging together...but now, the male is being very aggressive and nipping at the female and relentlessly chasing her around. I need some advice.
Get a dither fish for the tank. It'll take attention away from the female and bond them together in a way. Something like a small pleco. I had a clown pleco in my krib tank when I saw aggression between my pair. Now the pair, and 90+ of their younguns, some adults now, live together with the clown pleco.