Backyard Aquaponics
A place to discuss aquaponics

Hello, Im still quite new to this site and if my question has already been answeres I apologize just send me the link to that post I have (3) 275 gallon IBC's connected and feeding VIA SLO (3) 4'x8' x12" hydroton media beds. gravity returns the water from the tables into (4) 55gallon drums sunk in the ground plumbed together to form my Sump for the CHIFT PIST setup. Then the water pumps into another 55 gallon drum made into a biofilter. Im growing Tilapia and blue chanel catfish in Polyculture and started to get a fungal infection on my fish. I started using the water change with my well water at about 70% volume but found no improvement until I started to add aquarium salt at 24g per gallon (about 1 tablespoon by weight). I seperated the fish into a closed loop in the system and increased salinity in this "tank" only. Now the fish look much healthier and there are no signs of stress or any fungus. Here is my dilema, Should I just reintroduce the fish into the system WITHOUT salt? or will this low of a salinity reading not effect the bacteria cultures in my media and filter?

from my understanding some plants wont like the salt. Like strawberries for example. But the bacteria will be fine

Too much salt will knock out the bacteria. That is a given as I have successfully done so in the aid of saving the fish ( Barra ).....BUT...I used alot of salt !!! as I work on a salt mine so nothing was ever measured and it was free to come by.

If you are that worried about it slowly add water from the tank into the fishes temperary habitate so the are climatized to the conditions. When you feel happy with progress add the fish back into the main tank.

And Keep Testing the Water Quality. That is your indicator !!

My thoughts only and good luck with success

Thank you for the information. My lack of experience has definately started to show now that I have hit my latest series of road blocks, but with help from you experienced folks I hope to get it right. I am going to open the valves tonight between this tank and the biofiltering tank loop and hope everything keeps stable. I may be dreaming here but I was thinking if I test for nitrate before adding the treated tank into the cycle and again tomorrow about 24 hrs later then I should get some idea of how my bacteria are processing the treated water right?

You should be testing for ammonia and nitrite as they are both what is harmful to your fish and can tox the water quality

Can you post a photo of your system Our_Cheridise? It makes things a little easier to interpret. Many people have run salt in their aquaponic systems over the years. We are generally talking relatively low levels such as 1 part per thousand 1kg salt to 1000litres water. Food and Fish, from memory was running at 4ppt his system has worked very well
We often recommend 3 ppt and consider it to be an accepted method of aiding fish health.

Ive run mine at 3ppt for years

Yeah but is your bifilter still alive Charlie?

I hope so Faye....

Just found this interesting snipit from Diagnosis, treatment & prevention of the diseases of the australian freshwater fish silver perch (bidyanus bidyanus)


Any idea how much salt would cause this?

Also I have been testing ammonia morning and night over the period I added calcium hydroxide to the tank water to bring up the pH and I noticed that the ammonia moved up to 0.5. I stopped feeding for a day, but kept adding the calcium hydroxide but the pH did not drop. No other sign of what may be causing the increase in ammonia (ie no dead fish, clean bottom etc)
Anyone else experience this?

What was your initial pH.... and when did the ammonia rise.... morning/night... after feeding???

It's quite possible that by buffering your pH upward.. you increased the efficiency of the nitrifying bacteria .. giving a fleeting "spike"... was it gone by the next time you tested??


If you stopped feeding... as your ammonia was slightly elevated... then I'm not sure what you're trying to equate the rise in ammonia to...

But if you were still adding Calcium Hydroxide... and expecting your pH to "drop"... I can only assume you thought that it would do so... because feeding, and nitrification... would counter the pH rise from the Calcium Hydroxide...

Obviously... this wouldn't happen... if you stopped feeding... and thus input less to the nitrification process...

oops i meant the ammonia did not drop.

initial pH 5.5. Ammonia rise was in the morning before a feeding. It will always spike after feeding. Testing was done in the evening before feeding.

No the ammonia has stayed at 0.5 for the last 4 days (the period over which the calcium hydroxide was added)

pH is now 6.5 and I will stop adding the calcium hydroxide. At 0.5 the ammonia is not a problem at the pH of 6.5 so I'm not worried just curious

With a pH of 5.5.... your nitrifying bacteria colony... had probably "crashed".... hence the ammonia rise...

It's probably just taking a while to build the colony back up... essentially you're "mini-cycling"...

Out of curiousity... did you do any nitrate comparisons...

ie... have your nitrates fallen...

That had crossed my mind but with a kg of food going into the system when it was at 5.5 and the ammonia sat at around 0.25 i discounted that possibility.

Could the shifting the pH up have upset the nitifying bacteria a tad and as a result it is going through a mini cycling? Might test for nitrites tomorrow.

I definitely think that the ammonia rise is a direct result of a nitrifying "crash"... when your pH got down around 5.5...

And yes.. the "mini-cycling" is a direct result of raising the pH... but essentially beneficially...

The initial conversion of ammonia to nitrites prefers a higher pH than the nitrification of nitrites to nitrates...

And the latter nitrification....just as when cycling... wont begin until the ammonia has dropped to zero... (it's inhibited by ammonia)

So just as when cycling... you'll see a slight rise in your nitrites... and probably wont see any rise in your nitrates until both the ammonia and niotrites are zero... (discounting any residual nitrates)...

I'd actually increase your aeration if you can... to help the nitrification get re-established...