Backyard Aquaponics
A place to discuss aquaponics

Instead of filtering your tap water is it possible to add rainwater harvesting to your setup? If you get charged per gallon then it is cheaper to top up with rainwater too, besides the tap water chemical concerns you have.

FWIW I've never been concerned with our tap water for AP use, because to me unless there are heavy metals in it everything gets re-scrambled by the microbes anyway.

6.1 What levels of fluoride exposure are harmful to aquatic organisms?

The source document for this Digest states:

Fluoride did not affect growth or chemical oxygen demand degrading capacity of activated sludge at concentrations of 100 mg/litre. The EC50 for inhibition of bacterial nitrification was 1218 mg fluoride/litre. Ninety-six-hour EC50s, based on growth, for freshwater and marine algae were 123 and 81 mg fluoride/litre, respectively.

Forty-eight-hour LC50s for aquatic invertebrates range from 53 to 304 mg/litre. The most sensitive freshwater invertebrates were the fingernail clam (Musculium transversum), with statistically significant mortality (50%) observed at a concentration of 2.8 mg fluoride/litre in an 8-week flow-through experiment, and several net-spinning caddisfly species (freshwater; family: Hydropsychidae), with "safe concentrations" (8760-h EC0.01s) ranging from 0.2 to 1.2 mg fluoride/litre. The brine shrimp (Artemia salina) was the most sensitive marine species tested. In a 12-day static renewal test, statistically significant growth impairment occurred at 5.0 mg fluoride/litre.

Ninety-six-hour LC50s for freshwater fish range from 51 mg/litre (rainbow trout, Oncorhynchus mykiss) to 460 mg/litre (threespine stickleback, Gasterosteus aculeatus). All of the acute toxicity tests (96 h) on marine fish gave results greater than 100 mg/litre. Inorganic fluoride toxicity to freshwater fish appears to be negatively correlated with water hardness (calcium carbonate) and positively correlated with temperature. The symptoms of acute fluoride intoxication include lethargy, violent and erratic movement and death. Twenty-day LC50s for rainbow trout ranged from 2.7 to 4.7 mg fluoride/litre in static renewal tests. "Safe concentrations" (infinite hours LC0.01s) have been estimated for rainbow trout and brown trout (Salmo trutta) at 5.1 and 7.5 mg fluoride/litre, respectively. At concentrations of >3.2 (effluent) or >3.6 (sodium fluoride) mg fluoride/litre, the hatching of catla (Catla catla) fish eggs was delayed by 1–2 h.

Behavioural experiments on adult Pacific salmon (Oncorhynchus sp.) in soft-water rivers indicate that changes in water chemistry resulting from an increase in the fluoride concentration to 0.5 mg/litre can adversely affect migration; migrating salmon are extremely sensitive to changes in the water chemistry of their river of origin.

fluoride or fluorine is a tricky one as small amounts are actually used and fine but it is when large amounts accumulate it becomes a problem. Yea, I think it would be better if they skipped adding it to the water supplies and just provided toothbrush and toothpaste to the poor rather than making people drink it (seeing as it doesn't really help to drink it.)

Hum, I don't know if there is any good way to see if it is accumulating to detrimental levels. Some plants tend to be sensitive to it and other plants may tend to accumulate it more which would pass on more of it to the animals that eat those plants.

Wonder if there are any plants that are especially good at taking up fluorine that could then be removed and used as mulch on ornamental plants.

It did not take me long to realize my tap water was going to be nothing but trouble. My current rainwater collection consists of three 20 gallon buckets and three pieces of corrugated plastic 2x8 sheets. They sit on top of the buckets and lean up against saw horses. El Cheapo solution and yields plenty of water. As long as I keep my sump full, I generally have a little fresh water sitting around for top-ups. In a pinch I can still top up a bit with tap water, as the rest of the water is pretty clean.

If you are still wanting to build a slow sand filter, it could be used with rain water collection to make a very high quality of pure water. I plan on building one soon too.

Skip the tap water, and just start collecting the free stuff...

Hum, I don't know if there is any good way to see if it is accumulating to detrimental levels. Some plants tend to be sensitive to it and other plants may tend to accumulate it more which would pass on more of it to the animals that eat those plants.

Twenty-day LC50s for rainbow trout ranged from 2.7 to 4.7 mg fluoride/litre in static renewal tests. "Safe concentrations" (infinite hours LC0.01s) have been estimated for rainbow trout and brown trout (Salmo trutta) at 5.1 and 7.5 mg fluoride/litre, respectively

Yeah, everything I've read on it seems to confirm at best when it is applied topically it has some cavity prevention qualities. When ingested it can do a lot of nasty stuff including having links to bone cancer.



I've been looking, and if I find something, I'll be sure to post. I've read in some places where you can have water sample sent off for testing, but haven't figured out where yet. Would be interesting to find out more in depth, especially when we get the large scale filtration going.



Well, from what I am reading, even the plants that filter it out have issues. If it goes into the fruit, it is ingested anyways. If it's mulched, it goes into the soil where it can be picked up by other plants. It's a definite way of reducing it, that's for sure though, it just doesn't stop the fish from being exposed to it. I'm under the belief that if it's bad for you, then you should try to eliminate it rather than limit it. Your body has to work to get rid of it (like the liver), then it stresses those organs and makes it harder to deal with things like disease. I think the same goes for the fish.