Years ago we built our greenhouse/koi pond and planted a lemon tree . Since then we have added many fish and plants. Both have benefitted from our setup. There is a small pump in the pond that moves water up to the vegetable filter where the root mass of plant starts remove nitrates and waste.
Step 1: We Wanted Lemonade So We Built a Greenhouse With a Vegetable Filter
Lemonade goes well with our pizza...see https://www.instructables.com/id/we-wanted-pizza-so-we-build-a-wood-fired-oven/
Step 2: This Video Explains the Setup. a Vegetable Filter Uses Plants to Absorb and Utilize Waste /fertilizer From a Pond.
Step 3: Here Are More Images of the Greenhouse.
Step 4: Here Are Some of the Plants That Benifit From Our Fish Fertilzer.
The cacti are from seed and arboreal epiphytes grow like weeds in here. I have not had any blooms on the grapefruit so it is becoming root stock for other citrus that I'm grafting on.
Step 5: Here Is a Grapefruit Tree We Grew From Seed.
Using the koi pond water has made the plants grow great and kept the fish happy as we top off the pond with fresh water as needed. in the summer we water our hops and raspberries with the pond water so the koi give us raspberry ale as well as lemonade.....indirectly