Backyard Aquaponics
A place to discuss aquaponics

This is my first system and I need some general help. It’s a large system and I’m starting it up slowly and learning as I go.

When every thing is fully up and running I’ll have (4) 600 gallon (2,200 liter) fish tanks, 600 gallon surge tank, and (10) 250 gallon (950 liter) grow beds. Were using a 50 / 50 mix of expanded clay to river rock for the grow beds. It’s got 2 water pumps and a high volume air pump. The tanks are buried 3/4 of the way and everything is inside our green house.

I started running my system the first week of July. We started it with one fish tank, 2 grow beds, surge tank, and one pump. We added 20 feeder gold fish on start up and have been adding 10 every week; we have added 130 feeders and have found 12 dead for unknown reasons. We feed twice a day except the day we add fish. Two weeks ago we added a third grow bed when the nitrate levels got up to 10ppm. So far were only growing tomatoes and 2 types of lettuce.

I do water test twice a week. I haven’t seen any ammonia or nitrites since week 5. My PH stays between 6.8 and 7.2 with out adding anything else to help buffer it; right out of the well it’s 7.8. We have added cheated iron and trace minerals a few times.

Found a fishery about an hour away that I can get bass, carp, trout, and tilapia. They have a 50 fish minimum per order and will have 3/4” (1.9 cm) rainbow trout and striped bass for sale in 2 weeks but they want me to place my order next week.

Do you think I would re-cycle my system by adding 50 to 75 trout? I would add them to a second tank. How many would you add?
Should I start adding salt as a preventative till I hit about 3ppm with new fish coming?

By surge tank, do you mean sump tank?

What do you mean re-cycle the system? Sounds like what you have is already cycled at least to the feed rate of the goldfish.

3 ppt of salt would be good for adding new fish.

I expect you could add 50 trout so long as your water temp is cool enough for them and you have plenty of air going.

You can probably have 1 lb of fish per 5 gallons or flood and drain grow bed media. Or 5 lb per 25 gallons. I often like to count that as 1 fish per 5 gallons of flood and drain grow bed media. If you have 3 250 gallon grow beds, that would add up to 750 gallons of media. That will easily support 50 trout. You could probably even go up to 100 with a new system but I would not really recommend pushing up to 150 since it is still a new system and you are still learning.

Is your water staying cool enough already for trout? I wouldn't know since it is way too hot here for trout.

Yes the surge tank is a sump.

I have read that adding to many fish at one time can cause an ammonia spike and the tank to cycle.

I’m planning on starting more grow beds as needed based off nitrate readings. But your math looks good and I’ll get a fourth grow bed going a few days before I add the trout.

I haven’t had any water temps above 74*F or 23.5*C since the middle of August and they have been slowly dropping.