Well as with almost everything it comes down to money and when things go from good to bad the most expensive hobbies like this one are on the chopping block.
Here over in the UK we have a similar issue - large businesses forcing out the smaller ones, and generally people choosing less expensive hobbies or just living more 'virtual lives' which IMO is the saddest and most damaging change.
Sadly, I agree with your friend that the aquarium hobby has its days numbered although the most dedicated will still try and hang on, as most people, esp younger generations, have less and less expendable finances. The truth is this is a luxury hobby for easy times, and when harder times come around people focus on necessities.
Unfortunately I have a bad feeling that his time prediction of 10 years is far too optimistic. Consider two dates:
24/07/2020: US eviction moratorium expires
31/07/2020: Federal unemployment assistance to be significantly reduced (currently in debate)
The truth is a lot of these jobs & businesses on furlough/assistance don't exist anymore, it's just being propped up by Government debt payments. So very few people will soon have the left over cash to afford a hobby like this.
As financial markets are usually reactive rather than proactive, you don't usually see the knock-on effects until after a short delay. So wait for the Q3 & Q4 reports this year...