Utah Aquaponics System Part 14 - Hybrid Stripped Bass Fingerlings Problems
byon 03-19-2011 at 02:08 PM (160443 Views)
Originally Posted 21-July-2009
The replacement shipment arrived. This time in good health. There were 134 fingerlings in the box and only 1 was belly up. The rest were actively swimming and looked good. The water tested very close to mine, including temperature. I slowly exchange water for about 45 min. Then we netted them out, counting them as we put them in the tank. These guys are vigorous swimmers and eaters. They are fun to watch.
The next morning 12 were belly up, then 7 the next. I'm a little dense and but finally retested the water, Ammonia was 1.0, Nitrites .5 and Nitrates 30ppm. Who knows where it was the day before. I did a heavy watering of the other greenhouse plants, using up 10-15% of the water, replacing it with fresh water. The next morning the levels were back to normal, except nitrates, which are usually around 10ppm is up to 40ppm. So it probably would have cycled on it's own. If I had been thinking, I would have done partial water changes at least daily starting the morning after restocking for several days and tested twice daily.
I would not have thought that such tiny fish would have caused a 300 gallon system already cycled and populated with 100 bigger bluegill to spike so easily, but I was wrong. I lost another 9 over the next 2 days. I don't know how many days it takes for the affected fish to finally stop dying off, but the first batch stopped after about 5 days.
Now I have 140 fingerlings left + 100 Bluegill in a 300 gallon (1100 litre) Tank. That is to many at full size, but my goal is to eat the Bluegill before the bass get to big, making room for the bass to grow up. You can stock 1-2 Bluegill per gallon of tank (or about 1 per every 2 litres) and you can stock 1/2 bass per gallon (or about 1 bass per 7 litres). So at full grow out, my tank should handle 150 bass. Given an 80% survival rate, my 140 should have 110 left at harvest, that leaves a little room left over for a few bluegill.
The bluegill are easier to raise, but don't get very big. Full size is 6-8 inches (150-200mm) and 3/4lb (1/3kg). After that they grow very slowly and are not worth keeping. Bass will continue to grow after they reach market size of 1.5lbs (.7 kg). Bass are more finicky, they need higher dissolved oxygen and better water quality. The down side is that Hybrid Striped Bass are only available as fingerlings once a year in early summer. I may have to keep multiple tanks and split them as the older ones are harvested. Bluegill have another challenge, they grow at widely different rates, so not a very efficient fish to raise, but fun to catch and good eating. Unfortunately these are my choices in Utah.
The tank temperatures have been climbing as the daytime outside temperatures are reaching 100 degrees (36-38C). The tank which normally stays below 72 degrees (22C) was up to 74 degrees (24C). That's to warm for good lettuce growth, although everything else likes it, including the fish. I've started taking the insulated cover off the tank at night so that it can radiate more heat into the greenhouse cooling it down. If that doesn't work, I'll start freezing gallon jugs of water to put in the tank in the day.
Originally Posted 5-August-2009
This is a summary of my thread over in the fish section that I wanted to post here for those following my system.
The second batch of fingerlings started out well, but soon I was losing 7-12 per day! They appear to have had Flexibacter Columnaris (aka cotton-mouth, saddle back). Probably as a result of the stress of the move, a spike in ammonia as the system adjusted and contact with the prior fish which had already contracted the same as they were much more stressed.
Knowing what I know now, I would have treated quicker and with my final solutions. As it was, I netted most of the fingerlings (but not all, some where to hard to catch) into a 50 gallon tote, where I added an airstone and treated the water with 3 ppt salt and a triple sulfa from the pet store for 5 days. I also treated the main system by adding salt to 1 to 1.5 ppt (by checking with my total dissolved solids meter.) After I put the bulk of the fingerlings back in the main tank. I continued to loose fish at 1 to 2 per day AND I lost 2 bluegill.
I called a fish food supplier in our area and they only sale medicated feed in 50lb bags, BUT he suggested I call one of the hatcheries as he said they often mix small quantities. I called the hatchery where I purchased the fingerlings, they never treat with antibiotics, they put sick fish in 20 ppt salt water for 24 hours and repeat if needed. (It would kill the plants in aquaponics). They also said they know of hatcheries that mix their own medicated feed, they add vegetable oil to the pellets, then add the Terramycin powder and mix well.
Given this, I went to our local farm supply store and bought a packet of Terramycin powder, put a cup full of pellets on wax paper, added a tablespoon of vegetable oil, stirred well until all pellets were coated with oil, then added enough antibiotic powder to coat all the pellets and stirred till it was absorbed by the oil on the pellets. I repeated this process until I had about a 2 week supply.
I started feeding this 6 days ago, I lost 2 more fish in the first couple of days but after that the deaths have stopped. The fish are active and feeding strong. I'll continue to feed for 14 days (10 is the minimum). All signs of Flexibacter Columnaris are gone.
Before I could identify the Columnaris, I thought it might be reaction to elevated levels of Potassium that is supplemented as there are reports of Hybrid Stripped Bass not tolerating Potassium. I contacted several researchers and received copies of several studies. All of them do show low tolerance for elevated levels of Potassium, but no more so than rainbow trout. And in the studies, when the lethal level was reached, 80% of the fish died within 24 hours, not a few a day.
Next time: 1) If I can, I'll setup a quarantine tank, and run salt at 3-5 ppt for a week and see if there is any sickness. If there is not any sickness, add them to the main system and reduce feed until the ammonia cycles with the heavier load. or 2) If I don't have a way to quarantine, add them to the main system, at the first sign of sickness, begin feeding medicated feed and raise the salt to 1-3 ppt. Also upon initially adding them to the system, back off on the feed. Watch ammonia closely, do water changes if it runs up and let the system adjust before feeding normally.
As it is, I now have 98 Bluegill and 64 HSB in my system. Summer is past the peak, maybe next month I'll add a dozen rainbow trout just keep things interesting.
Pictures of the medication tank attached.
Note: I found that HSB are very sensitive to handling until they are over 8-10" long. Anytime I would handle them to check size or growth, several would turn up dead in the 24hrs after the handling. I did not have this problem with the bluegill or the rainbow trout. One technique seemed to help is to not feed the fish for 24hrs before you handle them, this reduced the loss.
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