The most notable thing about the fish since you last saw them is that they have grown 10 times their original size. They were in the 10-15g range shortly after I got them, at I’m guessing 3 months old, and they are 90 – 130g now. What seemed like a ridiculously under stocked tank a few months ago, seems well filled now. If you are considering a small aquaponics system with “just a few” goldfish, please have a look at Brutus in the top picture and imagine how he’d enjoy being crammed into a small aquarium (or worse, a bowl, but don’t get me started). My tank is 100 gallons, with roughly 150 gallons of water in the entire system. There are 11 fish in total. Goldfish will grow fairly rapidly until they are about 3 years old, but they do grow throughout their lifespan, which can be up to 20 years. Yes, you can stock an aquaponics system more densely than an ordinary aquarium, but fish still need room to grow and swim.
I’ve changed the diet back from the homemade gel food I blogged about earlier, to a premium pellet for a couple of reasons. The first is that I’ve been sick the last couple of months and I just haven’t had the energy to make the gel, especially since as the fish grew they were eating much more of it. The second is that I’ve found a really good Canadian fish food, Northfin, that contains relatively low-on-the-food-chain ingredients like krill, herring and sardines and no crap fillers. I picked up a small package at the fish store to try it out, and the fish seemed to enjoy it, but at $10 per 100g it was outrageously expensive. I was able to order a 2.5kg bag online for $80, which is still pretty dear, but should last a good while. These are well-fed fish, in both quality and quantity, and I’m sure that that, along with good water quality, explains their impressive growth.