Aquaculture makes a great hobby and some times a hobby can recover some of its costs.

However hobby means an activity you carry out for relaxation and enjoyment - even the taxman does not tax the benefits of a hobby - so long as it remains a hobby - a not for profit activity.

If you happen to swap some animals for some feed or other animals but do not actively seek to sell the fruits of your 'hobby' then it is unlikely that you could be taxed as you are not running an activity for financial reward.

By all means use your hobby to gain valuable experience and see if you really want the committment and risks of a full time Aquaculture business. Generally in Aquaculture it is difficult to convert the hobby status into a viable commercial activity without major investment.