I see. That's very admirable of you.
In your OP, you cited the "length 150 cm x width 60 x height 60 cm". I think 150x50x50 will be fine too. They are not particularly demanding swimmers, like say an iridescent shark.
No one can tell you with 100% certainty that no, your fish will never ever exceed 12" SL. We are simply talking probabilities, averages, expectations. No normal parent expects their child to grow to 7' tall but it happens
. Now, it is possible any one of us can slip and fall or get in a car accident but we still get up in the morning and drive too. Life's a gamble. If he surpasses 12" SL in, perhaps, 5-10 years, I am sure you will be in a different position by then, hopefully a better position to give him a bigger home, should you feel it is necessary... from YOUR experience then.
In your OP, you cited the "length 150 cm x width 60 x height 60 cm". I think 150x50x50 will be fine too. They are not particularly demanding swimmers, like say an iridescent shark.
No one can tell you with 100% certainty that no, your fish will never ever exceed 12" SL. We are simply talking probabilities, averages, expectations. No normal parent expects their child to grow to 7' tall but it happens
. Now, it is possible any one of us can slip and fall or get in a car accident but we still get up in the morning and drive too. Life's a gamble. If he surpasses 12" SL in, perhaps, 5-10 years, I am sure you will be in a different position by then, hopefully a better position to give him a bigger home, should you feel it is necessary... from YOUR experience then.