I bought my first silver arowana 6 weeks ago. My question is it it normal for them to lay motionless on the bottom of the tank and sometimes he sits motionless in the plants? I notice him doing this maybe once a week. He does it for maybe 30 minutes than he's back to patrolling the tank. seems odd but hoping this is normal? He is maybe four inches, appears healthy, eats good, etc. He is in a 90 gallon now and moving him to a 300 gallon in 6 months. Water perimeters: 0 Ammonia, 0 Nitrite, 20-40 Nitrate, Temp is 82F, Ph is 8.3. I know the pH is higher than ideal for arowana's but the LFS says people in the area keep them in high ph and have no problem. Thanks in advance.