Backyard Aquaponics
A place to discuss aquaponics

Any idea if these would be safe after thorough rinsing?

I'd say yes.

I use ex Hydrochloric acid ones.

They should be fine with a good wash out.

After the initial clean out, you might want to leave them full of water to soak for a while (this will dilute any acid left over in them.) Then drain that water away to the dirt garden before hooking up to the AP system.
Citric acid is pretty darn safe other than it's acidifying effect

I'd drink it!

Mmmm! ... Orange Juice!.....

Acids are water soluable
We drink citric acid a lot.
So diluted/washed out, it should be most fine.
The water may be a bit acidic if not washed properly, so add some shells. this will cause the acid to neutralise. Ummm don't know off hand what neutralised citric acid forms, but some ppl add lemon juice (citric acid) to lower their pH so I doubt it can be that bad.

Depends upon the alkali/buffer used. Most common would be calcium citrate.

And Vitamin C is supposedly good for fish health....

Well there you have it

But vitamin C is ascorbic acid, not citric acid.........

Slightly off topic but this is an interesting article esp with reference to citric acid as a additive to the diet of trout.
http://www.thefishsite.com/articles/475 ... -diformate
Perhaps a little lemon juice in their food, citric and ascorbic acid