Backyard Aquaponics
A place to discuss aquaponics

Hi,

I've just started in Aquaponics, having purchased a two growbed system and 1000 litre tank. I set it up at the end of October and filled it from my rainwater tank. At the time I added 10 goldfish.

Then in mid-November, I added 50 Silver Perch, each about 10 cm in length. At the start of this month, they started dying, one or two every couple of days; I now have 44 remaining. Five goldfish have also expired, but possibly because they were attacked by the Silver Perch(?).

Anyway, I purchased a test kit and ran all the tests - ph is 7.5; Ammonia is 0; Nitrite is between 0 - 0.25 ppm (closer to 0 I'd say) and Nitrate is 0. The tank has developed the brown algae (a thin film), and I never got to the "green water stage".

The odd fish seems to rub itself across the bottom now and then. Of the Silver Perch that have died, they have a few (up to 0.8 cm) "blotches" on them, but nothing I'd call "white furry material" like ich.

I feed them a couple of tablespoons of 3 mm fish feed pellets (which are all eaten).

What do people suggest I do to stop the fish dying? Is it possibly a fungus or ich, or lack of oxygen (although there is a 40 cm drop from the return to tank, and it has two airstones in it as well?

Many thanks,

Bill

I'd salt the system to 3ppt to start with (3kg pool salt) then tell us what happens with the fish

I'd go for some salt in your system Bill...

Ohh, I see Jaymie beat me too it.....

Ditto.... and what's your water temperature Bill?

Hi,

Water temp is 22 deg C.

What sort of salt would I use? Pool salt, table salt or what?

How long should I leave the salt in, and I assume at the end, I should do a complete water change?

Finally, what should I do (regarding water up to growbeds) as my growbeds are already quite productive, and I imagine salt water would kill the veggies?

Thanks again for the quick replies!

Bill

Sunray pool salt (seasalt) .... Bunnings has a 25kg bag for $5.92 at the moment...

3ppt is fine for most veges Bill ... strawberries struggle with anything above that...

Just leave it in there... the concentration will drop over time with water top ups anyway..

+1 for salt

Do you have an air stone in the FT.

Hi,

I have two airstones in the fish tank.

As I have a salt water pool, I'll use one of my Bunnings bags for the salt source.

What does the "+1 for salt mean"? Are you saying I should add 4 kg of salt instead of 3 kg?

Regards,

Bill

+1 is a short hand way of saying "yes I agree"... 3kg is good.

If you just top up the system wont the salt tend to remain the same? If you harvest plants salt could go with the plant, but I didn't think evaporation or transpiration would effect salt levels. Of course water changes as opposed to top ups will carry salt out.

Salt is absorbed by many plants, celery is especially good at it, I've eaten some very salty celery from a salted system.

Just added the 3 kg salt to the tank.

Celery is one of the veggies I'm growing ... I always like it with a bit of salt!

Regards,

Bill

If you lose 10% / week by transpiration/evaporation Novaris... then top up with 10% of fresh water... you will have reduced the concentration by 10%... exactly the same as a water change...

I would have thought as the water evaporated the salt concentration level would rise, as salt itself doesn't evaporate.
I can understand plants taking up salt though, thus lowering the salt concentration.

Lots of plants take up salt and other minerals in different amounts. There is a plant called salt bush that takes a lot of salt from the soil. Cattle love it so much that they are now replanting it in the cattle routes.