iAVS – Oklahoma – Hybrid BlueGill Fish Deaths

[Admin]

Hi Mike,

I hope you’re doing well! I just saw your post and realized I didn’t get a notification about it—sorry for missing that.

I’m going to share this with Mark and will take some time to think it over before getting back to you. From what I quickly read, it looks like the pH changes could be an issue. With your seven years of experience, I think it would be great to investigate this further together since your insights will be important in figuring this out.

Can you let me know if you’re adjusting the pH in another tank or container before putting it in your fish tank? Is that what you’ve done in the past? Have you always had low pH levels, or is this a new problem?

We usually suggest that any top-up water should be adjusted for pH and let settle before adding it to the tank. This can help avoid pH swings, which might reduce stress on the fish. A quick online search shows that a pH below 5.5 isn’t good for bluegill and can affect their health and feeding habits. It seems like the fish might have been managing the pH changes, but with the higher temperature reducing oxygen, their stress levels could have gone too high.

You mentioned your growing area is small, but since you’ve successfully managed for seven years, it’s tough to find the exact issue right now. Just looking at your setup (and forgive me if I’m wrong), it seems you have a 5,300-liter fish tank and a 1,440-liter grow bed, which gives you a fish tank to grow bed ratio of about 3.6:1. That’s higher than the recommended beginner ratio of 1:2. So, it looks like your growing area might be a bit small. I’m curious why this hasn’t been a problem before, but it could be due to two possible factors: the low oxygen levels combined with high temperatures and pH swings might have stressed the fish significantly, or there may be a buildup of nutrients to toxic levels from not having enough plants to balance the nutrients from the fish. Is the fish feed you’re using high in nutrients like copper and zinc?

My first suggestion would be to establish a good routine for managing your top-up water to keep the pH stable.

Secondly, consider increasing the size of your growing area and adding more variety in plants and their growth stages.

I should mention that I don’t have experience with degassing.

Dissolved oxygen levels could be low, especially at night, but since you’re degassing continuously, I’m not sure if that’s the issue. Maybe try running water over something like a cascade aerator and consider an extra irrigation event during the night.

Given your extensive experience without serious issues, I’m cautious about giving advice since your observations could help us understand the real problem. Maybe we can look into how your approach has changed this year compared to previous years. Have the temperatures been this high before?

A quick online check shows that consistent temperatures above 80°F (27°C) can stress fish, slow their growth, reduce the water’s oxygen-holding capacity, and cause them to eat less. Stressed fish are more prone to diseases, and warmer water can encourage harmful bacteria and parasites. If high temperatures persist without a break, it could lead to fish dying, especially if oxygen levels drop too low.

Is there anything you can do to cool down the greenhouse? Is the fish tank below ground level?

Normally, I’d suggest cutting back on feeding for a bit, but it sounds like you’re already managing that.

Dr. McMurtry said hello and best wishes, and his notes contributed to my response above, as well as his notes below;

Two potential issues first come to mind. He has not mentioned the prevailing dissolved Oxygen levels (and diurnal range). I know that reliable DO meters are prohibitively expensive to a non-commercial operator, but perhaps he could borrow or rent one from his local State Ag Extension agent/office. At those water temperatures this could easily be problematic- especially when combined with radical/rapid and pH swings. WRT to the pH swings (highly stressful to any organism), has he maintained sufficient populations of actively growing plants? and continuously? – to uptake the accruing nutrient load – and also to maintain an effective pH buffer via the rhizosphere. If he hasn’t, then various if not multiple elements may have accumulated to adverse levels – notably metals. Very hard to say what is going on since there are so many interacting variables. Even harder to know how/what to correct. I’d reduce feed to almost nothing, determine/improve DO, find a way to ‘automatically’ correct/regulate pH – on a continuous basis rather than intermittent rapid ‘bumps’ and grow MORE plants (as many as possible), particularly species with high nutrient demands. Wouldn’t be a bad idea to attempt to collect a representative soil sample – perhaps also the bottom layer separately- and submit to a State Dept, of Agriculture lab for analysis (every state has these and fees are not outrageous – or weren’t years ago). There really isn’t a substitute for data (information) when attempting to solve a problem.

Thank you for your patience, and I look forward to your response!

[Mike]

Hello Max & Mark !

Sorry for the really late reply, just noticed this a few days ago. My priorities have changed starting Labor Day, but now things are setting down again so the iAVs system is back on my ToDo List !

Regarding the pH of the makeup….I use City of Bethany OK water from our local city which is from wells and the pH comes to me about 7.8. What I have realized is that during various times of the year, especially during the “dawg days of summer” or when repairs are being made to the Bethany water plant, the city has purchased / supplemented with City of OKC, OK water. OKC water is extremely high pH, usually about 8.9 – 9.2. Both water supplies have used Chloramine, which I seem to be able to neutralize with 30 ml / 275 gallon in any IBC tank. After filling the IBC tank, my simple titration tester shows no chlorine.

The 275G IBC tank is trickled thru the sand beds overnight before the sump returns it to the fish tank.

I have added my winter plants to the system; I now have about (50) snap pea vines, (4) cauliflower plants, (5) broccoli, (1) cabbage in addition to the 3-year old cherry tomato and (1) kale that is 3′ tall and still producing.

The fish deaths have subsided, likely due to the cooler water temps. Obviously, I want to figure this out so that I don’t repeat it next year. I have always lost a few fish a month during July-August, but this year it was more like a fish or two a week.

Mark IRT testing – I have used our County Ag Service in the past to test regular garden soil, I just figured that sand testing might not be in their wheelhouse….do you have any suggestions, or can you advise me on how to collect the sample….?

NOTE: I have again tried to upload a photo, but I get the message “upload failed”

Thanks for the help………mh

[Mark]

Greetings Mike. WRT samples, Local Ag Ext shouldn’t care where a sample came from. If you’re growing in a media then they should consider it to be soil (albeit locally atypical). I’d take 4 or so samples about half way between the furrow and plant stem at a few inches depth. You could mix them to achieved the required sample volume but if cost isn’t a limitation, multiple separate samples provides for greater detail (identify potential range/variability). Generally speaking, one-off of anything isn’t ‘proof’ (reliable datum) of anything. I would also consider doing the same thing from the lowest few inches of the filter bed to determine what is or isn’t accumulating/migrating within the vertical column. Have you seen any deficiency or toxicity symptoms? I suspect that your summer deaths are the result of the combination of pH swings and DO reduction from elevated temperature. Stressors tend to not merely sum but multiply in impact. OTOH, as with people, old fish grow weary of the being weak, tired, sore and bored and so just give up. No one and nothing lasts forever.

PS. … No, the horizon is moving up! and watch out for sandstone buildings! Antelope Freeway 1/4 mile. (I’m no fun. I fell right over.)

[Mike]

Mark –

As good timing would have it, last week I had to repair the exit end of one of the beds due to a long-standing leak which finally was allowing too much sand to drift out of the drain slit. The bed has been in service for 8 years, wish I had used a better grade of vinyl liner.

Anyway, when I dug out a trench about 8″ wide the width of the 36″ bed to assess the liner, I was pleased to find that the sand was just as “sweet” as I day I filled the sand bed, about 8 years ago !!! Not a smidgen of odor…very exciting!

I had been in contact with the Aquaculture Dept at Okla State Extension, but their testing program is limited to soil. The advisor I traded emails with was familiar with media bio-fouling in aquaponics systems. I did my best to explain the beauty and robustness of the iAVs system with its anti-fouling qualities – which I could do with complete confidence – especially after having just dug out the 8-year old bed.

I think I would like them to run a battery of tests on a water sample that I will extract from the sand….if you think that would be worthwhile. Here are the tests they offer. Soil, Water and Forage Testing Services & Price List | Oklahoma State University

As always, grateful for your experience, expertise and real scientific methodology……Mike

(….and he walked into a great sandstone building, ohhhh my nose….)

[Admin]

That is excellent feedback, thank you.

I have had beds running for 2 years, and when I dug into the bottom layers that sand was, like you said, as clean as the day I bought it – 8 years is amazing.

With the soil tests, perhaps it would be better to send the samples in and don’t tell them where it came from, that’s what I would do!

As you probably know very well, when Mark did his research some of the horticultural people were a bit ‘funny’ about fish being involved…..it may be a similar issue with the soil tests.

– Max