but eventually they will simply outgrow the FT sorry

ive heard thats a myth gnash, fish grow till the tank cant support them anymore, then they die

fair enough still 35 tilapia in a 200L tank aint gonna grow big enough to eat

Isn't that a bit of an old wives tale that fish only grow to the size of their container?

Won't they continue to grow if the water quality is maintained?

I had a barra in an aquarium for 3 years...didn't grow bigger than 20cm in the whole time.....I'll work of what I actually have seen and done before listening to others myths

For certain types of fish this principle will hold true. The best example to demonstrate this that I think will be familiar to most people is the goldfish in the bowl example. Everyone has seen at sometime a little goldfish kept in a bowl, no filtration, just a fish and his bowl. That fish can live for several years and never really grow to more than 2” or so, but take that same fish and put him into a 2000 gallon pond and you will see a very different animal emerge, a nice fish growing up to 10” with long fins and vibrant color. WHY? Well, it has a lot to do with the volume of water the fish is kept in, however; there are many other contributing factors we can look at.
Nutrition places a big role in fish growth and health; if you are looking to get that growth you can use growth foods and/or look for foods with high quality ingredients. Fish foods that have the first ingredient listed as potato starch will not be as healthy as those with the first ingredient being fish meal for example. Good feeding habits for your fish are vital as well, do not underfeed or overfeed your fish watch carefully how your fish eat and adjust your habits accordingly. Temperature plays a role in fish growth, make sure that your temperature is correct for the type of fish you are keeping, temperatures that are too low or too high will affect growth. Water quality is probably the most important factor in growth and overall health, high water quality and filtration are a must if you expect to see normal and healthy growth patterns for your fish.
Stock levels in your aquatic environment are critical as well. Fish secrete a growth inhibiting hormone, as that hormone level in their aquatic environment grows to higher levels the growth rate of fish slows and/or stops. This explains that goldfish in a bowl; as that little fella sits in his gallon of water the hormone count in the water keeps his growth stunted even though he is genetically programmed to grow much larger, water changes can dilute that hormone or more volume of water will dilute that hormone as well. So, in one gallon that fish will get to 2” and grow no more, in 2000 gallons that same fish will grow to its actual size. An overstocked aquarium or pond will have high hormone levels inhibiting the growth of all the fish, as well as dragging down the overall health of all the fish. A correctly stocked or even a lightly stocked tank will yield better health and better growth for all the fish.
So, yes your fish will only grow as much as their environment will allow but it is controllable by way of how their housing and nutrition parameters are set-up for them.

We have a barra in our aquarium here that is well over 1kg.. Hmmm, need to do an experiment.