Growing fruits in large pots, need advise on improving drainage

Hi there

I have three large pots, their widths greater than 530 mm, and their heights vary (the shortest pot is about 500 mm tall and longest is about 800/900 mm tall). This is my first attempt at growing anything in pots this large. I’m growing berries and dwarf citrus for now, and I plan to add more fruiting plants once I’m comfortable.

I’ve filled them with good quality potting mix (richgro black marvel potting mix or ANL greenlife premium mix). Added a bit of seamungus and rooster booster pellets on top, and a little bit of compost.

Silly old me didn’t realise that once water is added (via manual watering or rain), it will need to travel longer distance down towards the drainage holds. And that not all water will drain away. This has made the pots VERY heavy, meaning a fair amount of water is being retained. I don’t think this is healthy for their roots in the long run. I think it will also attract gnats and other bugs as a result.

I am thinking of taking out the soil and adding a bit of perlite. I’m planning to leave the top 50-100 mm of soil as is, and mix in the perlite in the remaining soil.

However I’m not sure of the proportions needed. Can you please advise me how much perlite I should be using, how to mix in and if it will have any effects on the soil pH?