Backyard Aquaponics
A place to discuss aquaponics

I have what I believe is Columnaris in my tank and on my fish (I'm currently using fathead minnows) - cotton like substance that looks to envelope portions of the fish. I thought I had everything going well, but then the fish started getting this stuff and dying in droves!

Questions 1 - how do I safely remove this from the tank and fish as it is supplying 7 grow beds short of draining and sterlizing the tank?
Question 2 - has this compromised the food safety of my plants?
Question 3 - How do I ensure that this doesn't happen again?

Any assistance would be greatly appreciated as I have about 50 tomato plants about 7 inches tall that I don't want to loose! I already have a buyer from a local cafe for my tomatoes!!!

First, what are your water test results?
Temp,
Ammonia,
Nitrite,
Nitrate,
pH

what size and how old is the system? Is it fully cycled? What is your water situation, as in can you easily do water changes?

The fish you have, what is the salt tolerance of those fish? What is your system currently salted to if any? Salt can be an effective treatment against many diseases and it is just about the only really easy food safe choice.
Tomatoes can usually handle a fairly high amount of salt in a system.

(most fish treatments are not safe for either edible fish or the bio-filter and I would estimate that of the ones that might be ok to use on fish for consumption, most of them require a witholding period in clean water before they can be consumed. I don't know that any fish treatments (other than salt) are tested or presumed safe for the edible plants!!!!!!!!!!

Hopefully some one with more experience with fish diseases can come to your rescue.

In general, keeping the water quality has high as possible and fish as stress free as possible is the best method of controlling the diseases that get into systems naturally. Now I expect in the future you will choose to use quarantine as an additional method of keeping diseases out. When ever I get new fish, I keep them in a separate cycled up system for at least 3 weeks (usually 2 months) and after that quarantine period I can re-connect the systems together or transfer the new fish into the main system. Salt dips or salt baths can sometimes help save fish but you need to know what the fish can handle and stay with the fish during the bath.

water temp is 50
Ammonia .25
ph 7.8
nitrite .25
nitrate 5

I think the ammonia is creeping up due to the number of dead minnows on the bottom of the tank. Tried to scoop out as many as I could and stirred up the tank to try to bring them up. I always thought that dead fish floated....

First of all, are you absolutely sure it is Columnaris? If you are, it is caused by stress from crowding, handling, spawning, or holding fish at above normal temperatures. It can also be caused by injury. Since it is a common bacteria found in soil, water, and on the fish themselves, there is no need to sertilize your system- it is common in the environment and it can attack all species of fish, including marine species. However, the bacteria is opportunistic, like most diseases, so you need to find the cause of the outbreak and prevent it in the future. This info is from my very expensive book, "Fish Hatchery Management" so you know that the information is reliable.
Salt will encourage the slim coating on fish, giving them more protection, which is why it is used so often in aquaculture, as well as AP. Flathead minnows are similar to feeder goldies- they seem to harbor disease very well, although the biggest problem I use to have was White Spot. Remove the dead, coat the survivors will salt and the disease outbreak will die off by itself, once water parameters and population are within the fish's tolerance level. The tomatoes will tolerate some salt and may even give better flavor to the fruit and solar dried salt will also contain trace minerals. Sorry about your losses but fish kills of these kind are very common. These fish just don't go through the rigors of commercial food species and so introducing diseases is very easy. Don't worry about your tomatoes, they'll be fine- whether you salt or not. I hope this helps.

Is this and outdoor or indoor system?

50 F water is pretty chilly for cycling or if the system was fully cycled before and now the ammonia and nitrite are showing up might be due to the lower temps slowing down the bacteria.

Do as much as you can to improve the water quality. Salt up to 6 ppt won't hurt the tomatoes but you probably need to check on the salt tolerance of your fish since many fresh water fish will be hurt by 5 ppt or more.

Good luck

Thanks for the info! This is a system within a 10 x 12 greenhouse.

Our problem could certainly be overcrowding. We put 600 minnows in a 150 gallon tank so I'm sure we stressed them plus apparently there was a lone bluegill that was in the tank terrorizing the little guys!

Great to hear that it hasn't compromised the system and is just on the fish. We're removing the dead ones as they float up and have the aquarium salt to add (please tell this dummy was ppt is)!!!

Thinking about starting a breeding colony of tilapia in an aquarium. Since this is just on the fish, once we remove them all and let the salt cycle for a while, will the fry be okay? How long should we cycle the system after the dead fish are removed and we add salt before adding new fish? How long do you quarantine new fish? What would be a recommended stocking ratio for a 150 gallon tank of minnows or goldfish?

Sorry for all the questions - I'm still learning!

ppt=parts per thousand. If you are thinking in metric it is incredibly easy: 1 ppt is one gram of salt per liter. For us (or "for US) we are looking at 13oz of salt or 380 grams per 100 gallons. I like to go straight to 3ppt, typically by dumping it into the sump. Cheap sources are rock salt from store or water softener salt from hardware store (about $5/50lbs, I think).

Yep 1ppt is 1 part per thousand (1 gram per liter or 1kg per 1000 liters.) So ya gotta figure out the conversions, probably easiest to convert your water volume (total water volume in the system) to liters and then figure out how many kg of salt to add, use a scale to weigh it.

Dissolve the salt in system water before adding it into a tank with any fish.

Solar pool salt or solar water softener salt, generally the cheapest stuff is what to use. Avoid table salt.

Tilapia are hardy fish so long as you keep the water warm. I have not found them very easy to breed in an aquarium size tank. In any tank larger with access to the bottom, it is nearly impossible to keep them from breeding. When they are busy breeding, they are not growing. Small ones need high protein feed to grow well. Only go for the Tilapia if you can keep the water really warm. They might survive water in the 60 F range but they are not gonna be doing much for you or your system at that temp. And if the water gets down below say 53-55 they will probably start dieing of infections as their immune systems don't do well after they have been really chilled.

If you can keep water quality good and have enough aeration, I think Catfish are better growers than tilapia unless you have a really cheap source of heat for your system. I've heard that blue gill are good fish to grow too.

I plan on putting a screen in the bottom system tanks so the eggs will drop through. I've read of people using 100 gal aquarium for breeder colony for tilapia. I like the tilapia for the simple reason of producing my own brood stock seeing as they are mouth brooders and don't need too much for nesting. From what I've researched, a couple of flower pots for the male to occupy.

Tilapia are easy to breed (generally thought as too easy) I had some breed in the cage even when I was silly enough to leave a bit of pipe down in the bottom of the cage, they used it as a breeding surface.

However, breeding is only so easy if the tank can be kept quite warm. 86 F is a good breeding temperature.

And growing out tilapia does require warm water, otherwise it is kinda a waste of resources.

FYI (catfish are probably pretty cheap and easy to get in your part of the world.) I can get 3-5 inch channel catfish fingerlings for 30 cents each or 5-7 inch and larger for 60 cents each. I'll probably be getting 100 new channel catfish fingerlings here soon. Usually just takes a phone call and a drive down to the fish farm.

Or if you wish a fish that can reproduce for you, I've heard blue gill will do it in a large AP system though I have not tried growing blue gill myself.