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Rain water problem...
February 14, 2016
7:12 am
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Okay, so I collect rainwater for my tanks, since my tap water isn't great and having access to rainwater helps me modulate/control the pH of my tank water far more easily.

Unfortunately, the landlord has decided that there was too much moss on the roof, and has applied moss killer to it. This was one week ago. Luckily, my collection apparatus was not assembled, and I have about 100 gallons stored, but I'd really rather find a way to remove the moss killer from the roof than spring for an RO machine.

I found the container when he was done, and the active ingredient is zinc sulfate (ZnSO4). It would be fairly easy to simply hook up the garden hose and spray down the portion of the roof that sends water to my collection apparatus, but I don't know if that would be sufficient to remove the damn stuff.

So far, I've come up with the following ideas:

- Spray down the roof, a lot, and test the water until it appears to be safe

- Rinse the roof with tap water mixed with large quantities of water conditioner; the idea here being that the Disodium EDTA would help remove the Zinc

- Rinse the roof with humic acid/blackwater extract. I have a large bottle of this stuff that I use to help maintain blackwater conditions (I have a few Parosphromenus sp., and it helps keep the pH really low), and while it would stain the roof for a while, it would probably help remove some of the Zinc.

- Acquire some phosphoric acid and rinse the roof with a dilute solution (kind of risky; screwing up the concentration could cause other problems)

Anyone else had to deal with this before? I read that when left alone this stuff can take years to leach out of roofing shingles, and I'd like to at least attempt to remove it instead of having to buy an RO machine.

February 14, 2016
6:40 pm
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BillT
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I don't know much about washing that stuff off but, it sounds like you may be keeping your fish in soft water. If so, this makes your problem more difficult since copper and zinc toxicity goes up in soft water and is reduced in hard water.

If you can get hold of some of the material (or perhaps look up its chemical properties) you could see what might dissolve it before trying to do the whole roof.

 

From my experience running a research zebrafish facility, I know zinc and copper can have adverse effects on zebrafish down to fractions of a part per billion concentrations (both chemicals present at the same time, so might not be so bad in your case) in soft water (below 30 microS of conductivity). The test for these levels cost about $100/test (about 10 years ago).

I would expect these chemicals to affect molluscs also (probably more so) so I would try using snails as a bioassay for the chemicals after you try to remove them.

Bill Trevarrow [email protected]
February 14, 2016
9:11 pm
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BillT said
I don't know much about washing that stuff off but, it sounds like you may be keeping your fish in soft water. If so, this makes your problem more difficult since copper and zinc toxicity goes up in soft water and is reduced in hard water.
If you can get hold of some of the material (or perhaps look up its chemical properties) you could see what might dissolve it before trying to do the whole roof.
 
From my experience running a research zebrafish facility, I know zinc and copper can have adverse effects on zebrafish down to fractions of a part per billion concentrations (both chemicals present at the same time, so might not be so bad in your case) in soft water (below 30 microS of conductivity). The test for these levels cost about $100/test (about 10 years ago).
I would expect these chemicals to affect molluscs also (probably more so) so I would try using snails as a bioassay for the chemicals after you try to remove them.

Yeah, the increase in toxicity is my main concern here.

Using snails as a bioassay is a great idea that I didn't think of; I have an overabundance of pond snails at the moment, so it would be very easy to set this up. I think I'll try spraying the roof several times and then using the snails as an assay.

February 14, 2016
10:30 pm
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Byron Hosking
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Rainwater is ideal for soft water fish species provided the source is safe.  But rainwater should absolutely never be collected from roof run-off.  Chemicals from the shingles and animal excrement (bird, squirrel, racoon, rats all scamper over roves) are major issues.

The only safe method is to place a large container out in the open, away from trees.  If one is really serious about collecting rainwater, a large collecting container could be constructed.  But never use run-off from roves.

Byron.

Byron Hosking, BMus, MA Vancouver, BC Canada
February 15, 2016
1:18 am
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Byron Hosking said
Rainwater is ideal for soft water fish species provided the source is safe.  But rainwater should absolutely never be collected from roof run-off.  Chemicals from the shingles and animal excrement (bird, squirrel, racoon, rats all scamper over roves) are major issues.
The only safe method is to place a large container out in the open, away from trees.  If one is really serious about collecting rainwater, a large collecting container could be constructed.  But never use run-off from roves.
Byron.

 

You know, I've read this more than a few times, but I'm not having any problems doing it this way.

1) I live in an area without much industrial activity (for now...).

2) I clean the roof frequently with a push broom and if I find animal feces I rinse them away with tap water and don't collect anything for a few days while the rain finishes the job. It's worth noting that I have found animal feces once or twice, and it's pretty hard not to notice (house isn't large, is single-story).

3) The shingles are old enough at this point that any hazardous compounds are long, long gone. "Normal" shingles don't release toxins forever. The part of the roof that drains into my collection apparatus is also away from any trees.

4) I've been using this stuff for over a year at this point, in some tanks almost exclusively, and I've had absolutely zero problems with anything. I also keep a few orchids and carnivorous plants that receive water from the same source, and I have no problems there, either. I even have a bunch of freeloading daphnia, snails, bloodworms and other critters in my storage barrels, and I've seen no die offs, ever.

 

I understand why I need to be cautious, but I think this is a scenario that needs to be considered on a case-by-case basis. I actively work to keep my roof clean and I live in an area without a lot of air pollution, so I can collect rainwater from my rooftop without trouble. There was a long period of time during which the water I was collecting was crystal-clear without any settling particles, and it took nearly six months to change; just before the moss killer was applied my collected water was getting very slightly cloudy.

February 21, 2016
1:59 am
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Alright...

I thoroughly rinsed the part of the roof that contributes to my collecting apparatus, and allowed the roof to be rinsed again by some heavy rains recently.

I collected some more water for testing. pH was 6.4 - 6.6, which is normal (I've tested it prior to the moss killer application and had similar results). Regretfully, I do not have access to a TDS/conductivity meter, but I've ran one bioassay with snails (unknown species; they're not planorbids or thiarids; I think they are lymnaeids but they grow much larger than "pond snails"); there have been no deaths within 36 hours, and the snails are not acting stressed.

Bill T, do you have any experiences running a bioassay like this with snails? It's not rocket science, but I want to make sure I did it correctly before I blithely assume that the water is safe.

February 21, 2016
4:35 am
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BillT
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I have used larval zebrafish (1-5 days old) for bioassays (in a lab where there are thousands available). Any reasonably sized fish you are not too worried about losing could work for this purpose. Medaka and fathead minnows are used a lot for bioassays also.  Daphnia are a classic critter for bioassays. They also breed frequently so all developmental stages might be present.

Molluscs are reputed to be sensitive to copper/zinc which is why I suggested them.

 

Conceptually a bioassay is pretty simple. A negative control could be helpful of you do find some positive results to your assay (to rule out something like contamination from something other than the test water, but it doesn't seem you need it.

 

Other than what you are doing all I could suggest is to give them more time or try some snail eggs (maybe they will lay some). Embryos are often more sensitive and might respond at lower levels of contamination.

Bill Trevarrow [email protected]
February 21, 2016
10:11 pm
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BillT said
They also breed frequently so all developmental stages might be present.
Molluscs are reputed to be sensitive to copper/zinc which is why I suggested them.
 
Conceptually a bioassay is pretty simple. A negative control could be helpful of you do find some positive results to your assay (to rule out something like contamination from something other than the test water, but it doesn't seem you need it.

I have a 10 gal. tank outside full of daphnia, copepods and other things I caught from a vernal pool that I've been using to supplement feedings.

I thought of using them for a bioassay when you brought it up, because they're probably more sensitive. I'm just reluctant to do so because they're really useful as a food item and I don't want to "waste" them.

But I want to be sure, so I think I'll try that next. Thanks for the advice.

February 26, 2016
7:08 am
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Update 3.

I performed another bioassay with a variety of vernal pool invertebrates that I use to feed my fish.

The invertebrates were mostly cladocerans, but there were also two different species of ostracod and some copepods.

After being immersed in the rainwater collected from the roof for 24 hours, there did not seem to be any adverse effects, aside from perhaps some empty bellies due to be separated from any kind of food source.

After reconsidering the scenario, it is entirely possible that I was lucky and the landlord did not apply any moss killer to the surfaces that drain to my apparatus. That part of the roof is west-facing and has zero canopy cover; any mosses growing there have no shelter and dry out completely in hot summer weather, while most of the other surfaces have nearly complete canopy cover and have noticeably more moss growing between the shingles.

So I guess I was lucky. I'd also like to add, again, that while it is true that there are potential pitfalls in collecting rainwater from shingled rooftops, it is entirely safe if:

1) The roof is kept clean

2) The roof is kept free of animal feces, or frequent inspections show little or no fecal matter present.

3) The surrounding region has relatively low levels of air pollution

4) The roof has not been treated chemically in any way for at least several years

5) There are no copper or zinc strips on the roof (another popular anti-moss [bryocidal?] measure).

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