Backyard Aquaponics
A place to discuss aquaponics

I've got a 2600 gallon Brook trout fish tank in my system. I want to add salt for fish health, but am unsure what quantity I should be adding. I have a refractometer (I haven't used yet ) to test the current salt level, but really have not added salt on any kind of dosing schedule. I threw a handful of aquarium salt in a few times over the last two years, and want to get a scientific based handle on this. It's time I take this seriously, I know. Currently we've got ten or so two year old trout, which we'll be removing after Summer heat is over so we can start a fresh batch of fingerlings in Fall. Does it matter on the age of fish? Should I be using ppm or ppt? Total volume including sump and GBs?

Hi Brian,

I'd use total volume of water. 1 part per thousand is what I've heard for salting for fish health but it's based on what I've read on the forum. That's 1 gm NaCl per 1000ml and 1000ml is one liter. 3.785 liters per gallon (US). Freshwater usually has very little salinity and while I've seen higher amounts recommended on aquarium sites than what we give, I've also seen where this can be a problem for the plants in AP. I suspect we don't even need 1ppt since most freshwater doesn't contain this much and you may not need to add any salt (depending on the refractometer results).

I'm not sure if the fish age matters .

I'd reckon the older fish would handle lower quality water better than fingerlings.

If you do not have any issue with the fish's health there is pretty much no reason to add salt that I can think off. I usually added salt when introducing new fish, or when getting close to the Trouts maximum temperature when approaching summer to reduce stress.

i try to keep mine between 1 & 2 ppt, generally I use pool salt. the local pool store is happy to test the salt content for me.

thanks Scotty435.
Wow 1 gram salt per liter of water! I've got something like 12000 liters of water.
That'd be 12kg salt, Right? Holy cow! Or did I do another math mistake?



I'm still in shock over the quantity of salt needed to hit 1ppt NaCl in total volume.
I was imagining a quantity so very much less. I am glad I finally asked this question. I guess there is some other reason our strawberries aren't growing.
I'll take your advice on this and only dose salt if a fish health issue arises. I seem to recall reading there are other types of salt, such as Epsom salt which I assume has other minerals in it.
I'll do a chemistry test on the AP ASAP and see where the KH & GH stand. I hadn't done a water change in the AP this year, and hope the pH has stabilized from the high range of 8.4 pH it usually goes to after coming out of the well at 7.6 pH.
From the looks of our plants this year over last it seems we have improved mineralization.
There are still a lot of gray areas in my mind concerning our setup much like the salinity, such as conductivity which I am also only scratching at the surface of understanding. It was eye opening to realize photosynthesis, biology, chemistry and my chosen career of electronics have so much in common. I imagine there is a correlation between salinity and conductivity?
Also OutbackOzzie I gotta ask having seen you post after three years absent, have you found gold on the new place? Old school hippie artists such as myself always imagined you guys had hunks of opals lying around for the gathering?
I feel blessed to get your attention, thank you.

Those ions floating around in your AP system have charges

I'm ecstatic about that Scotty