One of the passed away friends for lemon trees used pvc piping to go deeper into the deep roots area for watering. Saved water instead of having to soak the ridgeline that drained fast. Might work for you too.
If needing readily available nutrients Masterblend works well and you just add water. Takes a 7+ ph water down to around 6.5. Morgancountyseeds sells the stuff the cheapest I've found. There's many mixes to choose from.
Great suggestion chopping up the fish to speed breaking down.