Backyard Aquaponics
A place to discuss aquaponics

Hi everyone my name is Barry and I am delighted to be a new member of the aquaponics world. I have recently built a system at a local high school. The system is about 400 gallons (I will try and get some pictures up soon) with a GB that is 4' x 7' and 12" deep. We did the math and I think we are under the 1:1 ratio but had no intention of stocking to the FT's capacity any time soon. We did a fishless cycle and it went well the ammonia and nitrites went down to 0ppm and the nitrates were at about 80 ppm. Just to be sure I spiked the system with ammonium chloride to 1ppm to see if the bacteria would take care of it in 24 hrs and it did. We added 50 very healthy and more mature tilapia fingerlings (These fish are about 5" in length so I guess I might have to call them fish now.)
They have been in for 4 days now and seem fine they are a lively and hungry bunch.
The system when they were introduced was

Ammonia 0ppm
Nitirte 0ppm
Nitrate 40 ppm
PH 6.8

After 2 days
Ammonia 0ppm
Nitrite .25ppm
Nitrate 80 ppm
PH 6.8

And on today Day 4
Ammonia 0ppm
Nitrite 2ppm
Nitrate 80ppm
PH 6.5

The nitrite spike is causing me concern and don't plan on feeding them tomorrow. But more importantly I am not sure what my next move should be. Should I feed the fish less ( I have been using the 5 min rule and they seem very hungry) Or do I need more plants in the GB? The plants I have are getting bigger every day. Or am I just being a nervous Nelly and worrying over nothing?
Any help would be greatly appreciated.

Thanks

Hi Barry,

Welcome, nice to have you aboard.
I generally feed my fish on a 3 minute feed cycle, about three times a day. I don't have Tilapia, Silver Perch and Rainbow Trout.
The perch slow down in our winter here, but the trout are gluttens, but they are fast growing fish.

The nitrate spike shouldn't worry you all that much. Plant numbers are a little hard to judge with no pictures, but you can get carried away with water checks all the time and worrying yourself sick over nothing. I check mine maybe once a month, but there are many here that don't check water condition at all. PH looks good and don't forget the plants need nutrition to grow and bacteria need nitrites to convert so it looks fine to me.
If it gets to hight levels of nutrients, you could always add another grow bed. ( maybe not as big if you like depending on area constraints )
You have a large fish tank so you could have more growing area which would use more nutrient.

Not too much to worry about here, things are just settling in since you added the fish. If you're really concerned, (pool) salt to 1ppt to mitigate nitrite exposure. Lay off feeding the fish until the nitrites drop again. Nitrate 80ppm => more plants!

Welcome Barry.... as Bunson posts... just hold off on the feed until the nitrites drop...

And salt to 1ppt in the interim...

Thanks for the advice guys. I put a bunch of seedlings in today and stopped feeding nitrites have risen to what looks like over 5ppm ( that's as high as the api kit goes) but I expected higher levels since I tested the water yesterday after I gave the fish a healthy breakfast. They are still very lively and keep coming up any time I peek my head over the tank. Hungry little guys.
I am hesitant to do the salt if i can avoid it for the plants sake. (It will just stay in the system no?) I attached a before picture of the GB and Whole system as you can see the left hand side was not planted in ( a design flaw on our end) but I got a board and a light person and threw them both up there to transplant more on that side. I hope this works, fingers crossed.

Current readings as of today

PH 6.6
Ammonia .25
Nitrites >5ppm
Nitrates 80 ppm

Thanks again

Your system looks good! I love the ingenuity of it! But, I'm just wondering why did you put the growbed up so high? Coming from a short person, my ibc one is hard for me to reach
I just wondered if there was a benefit to it?!

Stop feeding and change out 1/3 - 1/2 of the water with clean de-gassed water, today. Nitrites that high are going to do irreparable damage to the fish.

<pondering>A few dead plants, or, a tank full of sickly or dead fish...</pondering>

Sodium is a necessary element for healthy plant growth, salt (NaCl) is an essential mineral for many plants, in small doses. Although some people will argue about the numbers, the only plants I have had which complained strongly about salt was strawberries; if I added as much as 3ppt they all withered and died, whilst no other plants seemed to notice the salt. Some people have salted their systems higher and their strawberries survived; cest la vie.

Dosing to 1ppt helps fish deal with high nitrite levels, and you have high nitrite levels. If you don't add a little salt now, you will be salting to much higher levels later as the fish's immune system becomes compromised as they start getting diseases and fungus etc.

I'd also consider running the pump continuously and adding more air to the FT.


Scott

Oh man. I will change the water first thing and add the salt. What is 1 ppt? Like 1 1/2kg?

1ppt... is 1kg of salt per 1000L...

And 1ppt is all that is needed to mitigate against nitrites...

Bunson is right...strawberries are most sensitive to salt... and anything beyond 2ppt will effect them....

Most other plants will handle up to 6ppt... for the short duration that might be necessary to salt to those levels... which are usually diluted over the weeks by water top ups anyway...

Ok now I am completely confused I ran to the school to get here as soon as it opens and I started pumping out the water. While I was doing that I checked the nitrite level just to see if went down a bit and that I didn't compromise the bacterial colony. I checked it 3 times and each reading said 0- .25 ppm closer to 0 I would say. I even checked the water I was siphoning out. The has dropped some more between 6- 6.4. The fish seem fine. I through in a pinch of food and they went for it. My next thought is to buffer up the ph (I have ph up or do you suggest an alternative?) and leave it be. I did not add the salt although I will if needed. Just slightly confused.... Any thoughts?

How confident are you in the nitrite 5.0+ test from the previous day? If you get any extreme reading, do at least a couple tests and compare the results to validate them, then do another test against a baseline (distilled water is a good choice). I doubt the ability of any new system to drop from nitrites 5.0+ to almost zero overnight, but it could happen?

You can add chemical solutions to increase the pH, but I prefer a more natural solution, sea shell grit or limestone. From another thread:

There's obviously a lot of action going on in your system, so whatever you're going to do, I'd be doing it slowly to avoid swinging the system too far in any direction. I'd still avoid feeding for two or three days, reducing the affect of the nitrification process on pH and allowing it slowly increase naturally, with the addition of a pH buffer.

Check the manufacture dates of your water testing chemicals/indicators (I found out today some of mine are "expired" so it's timely advice?) Give your test equipment a thorough cleaning with a mild soap and rinse well.

I didn't double check the 5ppm that day I just took it as is considering I had a 2ppm the day before and took that reading just after I had given the fish there breakfast. But I am going to check the test kit and rinse every thing with a mild soap.

As for the design question from Pioneer Lady we were so worried about the overhead GB being a problem with harvesting the fish that we created a growbed access problem. I am 6'1 and have a hard time reaching parts of the GB. Live and learn

I will still hold off on feeding and report back.

Thanks again

Sorry to have been away so long but things at the school are really moving along. The nitrite problem has left and I am now just working at getting the ph up. I get it up to 6.4 and when I come back the next day it is back down. I have halted feeding again to help with bringing the ph up. I was using ph up but many of you suggested other things. I can't seem to get my hands on any potassium carbonate. I plan to order some online.
The best I could find was dolomitic lime that a local garden and hydroponic store had. It was a big bag of powder so I thought a tsp in the tank and wait and see. I know Bunson you suggested limestone and I have read also about hydrated lime which I think is even more concentrated than dolomitic lime but I might have made that up in my head. I like the dunk bag idea the last thing I want to do after all this is sky rocket the ph. I am just not sure how fast or slow dolomitic lime is. I will check back tomorrow evening and see. But is this something I can add and than check back in a couple of hours to see.
One last peculiar thing is that the nitrates have been a steady 80 ppm throughout all of this. I tested the kit against tap water and got a 0ppm reading and cleaned everything out. Could the plants be locked out of the nitrogen?

Readings as of today
ph: < 6.4
Ammonia: .50ppm
Nitrites: 0ppm
Nitrates 80ppm

Dolomite Lime... is Calcium, Magnesium Carbonate... it will do the job, and the magnesium will benefit the plants...

But Calcium Carbonate, (lime, shells, coral, shell grit) is probably better....

Hydrated lime... Calcium Hydroxide... is more powerful... works faster, and raises pH faster (beware, small increments)....

Potassium Carbonate... would work the same as lime, or dolomite... but provide a Potassium boost rather than Calcium... good for fruiting/flowering stages of growth...

Potassium BiCarbonate... as above... and also good as a fungicide, and powdery mildew treatment... (look in wine making supply stores, or online)...

Your pH keeps falling back... because your system carbonate buffer is exhausted... and eventually any buffer you add becomes depleted as well...

Perhaps sprinkle some shell grit through the grow beds... or hang in a sock under a water return.... it's a slow release, self regulating pH buffer...

Your nitrate levels suggest that you could/should add more plants...

If you don't have room to...then your readings, including your continual pH decline... suggest that you are on the edge of your filtration capacity...with your feed rate...

And you either have to add some more grow beds... or take out/eat some fish....