Hoi, nog een Nederlander hier!
Tank size really isn’t a problem. I have a lot of fry growing fine alongside Betta strohi in 160 liters. I dared to try this because it is the sp. Sentang, which is quite common so no big deal when the fry wouldn’t survive. This tank is full of Ceratopteris, which is, in my opinion, perfect for rearing fry. In contrast to javamoss this plant rapidly dies and grows, producing al lot of waste which is consumed by small organisms, which in turn are a perfect food for fish fry. This is a lot more like how it happens in nature.
It appeared to me these fish are actually quite easy to breed with a lot of Ceratopterus. The tank is not even really acidic and I feed mainly frozen food.