What method do you suggest for full protection of the human operating the tank? Tank inhabitants aside.
Ignoring nuisance trips and ground probe debates and focussing on HUMAN safety:
What follows are my thoughts on this subject. You should ALWAYS seek the guidance of a qualified and licensed local electrician.
At the very minimum I would suggest ground fault protection (RCD in other parts of the world) for all of the equipment that services the aquarium and receptacles that are close to the aquarium, regardless of use. Either breakers or receptacles. Both are effective.
In fact, I would suggest that people who can afford it, hire an electrician to upgrade breakers in their panel to AFCI/GFCI types as prescribed in the current NEC code. The rules evolve over time and are based on historical data regarding shock, electrocution and fire. The rules are not retroactive, so it is up to you to request upgrades.
Arc fault circuit breakers add a protection against arcing shorts. They could detect some power strip failures.
Many power strips fail because they melt and catch fire before the breaker sees enough current to trip. The culprit is often salt creep either direct or due to evaporating drips. The arc fault breaker may or may not see this, since AFCIs detect line-to-neutral or line-to-ground arcing but not always carbon tracking or parallel leakage through salt. The later is a common cause of failure. The parallel leakage through the salt (the same as carbon tracking) produces tremendous amounts of heat without tripping the breaker. The heat melts the power strip, allowing the contacts to loosen, generating even more resistance and heat. The result is often an non-arcing fault that creates a fire. Commercial quality power strips can help to reduce the risk. They have a metal frame with real NEMA 5-15 receptacles instead of soft plastic bodies that hold cheap copper bus strips. the metal frame is grounded and will trip the GFCI and the UL rated NEMA receptacle will not melt (nearly as easily).
A ground probe (only if you have GFCI protection). This will allow the GFCI to detect fault current in the tank and trip the breaker before you ever put your hand in the water. Without GFCI protection, a ground probe increases hazard.
Use only actual UL/CSA listed equipment and avoid China knock offs. While they may have agency listings, they are often fake. You should be able to find the UL/CSA listing for the device at the agency website. Also be aware that many manufacturers will use a UL listed component and build their unlisted device around it, then fraudulently display the device as listed. So stick with well regard name brands with traceable certifications.
As mentioned above a simple receptacle tester can confirm polarity and basic miswire. If you find an issue, call an electrician. This is very important if you have more than one circuit feeding your aquarium. If the circuits are on two different legs from your panel then there is 220 V of potential between the hot conductors, not just 110 V.
While balancing load to the panel is important, I would recommend that if you are going to use 2 or 3 branch circuit breakers for redundancy, that they be on the same leg. This limits fault voltage potential to 110V.
Always be aware of the risk. Test GFCIs regularly. To be sure, the "test" button on a GFCI does test the device by sending fault current through the comparator. If the test button fails, the device has failed and needs to be replaced.
Be aware of your surroundings. ALWAYS Inspect for salt creep, leaks, UV damaged or physically damaged wires.
Use the one hand rule when possible. One hand in the tank, one at the side or behind the back. Stand on dry, insulated flooring. Shocks are unpleasant, but a shock through the arms crosses the heart and can be deadly, even at low current.
Note that the uninsulated body (bare feet on concrete, arm in the tank for example, ) would allow the GFCI to trip of no ground probe were used, but that is a risk not worth taking. Use the ground probe to route fault current, not potentially (no pun) your body. Without a ground probe and with an insulated body, the fault may not clear (trip the GFCI) but you don't get shocked either.
Never ground the tank to multiple different grounds or an isolated ground. The ground probe MUST go to the ECG (ground pin or wire) feeding a receptacle. If there us more than one ground probe, ground them all to the same common spot.
Assume that epoxy potted pump motors (cheap power heads, AC magdrive pumps, etc.) will eventually fail and may create a fault if submerged. So plan to replace them on some fixed schedule before they shock you or trip the GFCI.
NEVER fully submerge the head of a heater. The heater should be placed in a fixed water-level compartment with the head out of the water. Prefer heaters that have a test tube shape instead of those with two open ends that are plugged. NEVER allow a heater to run dry. If it does, throw it away.
Circuit breakers are not meant to protect you. They protect the branch circuit wire. GFCIs are meant to protect you.
Lastly, where possible use low voltage DC equipment. While DC is still dangerous, many of our DC devices pose far less risk than their AC counterparts. This goes back to cheap China stuff though. Ensure the DC power supplies are properly isolated. Cheap converters with AC leakage are dangerous. So avoid the $10 wall warts and use reputable DC supplies (Meanwell for example).
