Your views please!
I have been experimenting with various systems for breeding Zebra Danios. The often-quoted 'marbles' options seems reasonable for domestic set ups but I wonder if anyone has tried using polyacrylamide balls instead of marbles? The Polyacrylaminde balls are sold for use with cut flowers. They are apparently non-toxic. If you haven't seen them, they are tiny beads which swell to many times their size on absoption of water and feel like frog spawn to the touch. They are a fraction the cost of marbles, they are softer and seem like a great option. But I can't quite bring myself to trust the claim they are "100 non-toxic"!!

What do you think?

Can't comment on their safety, but I wouldn't personally risk it. Just use spawning mops or use large pebbles in place of marbles.

In fact with Zebra Danios if you put a group of 6 or so in a tank, watch for spawning behaviour and take the adults out within a couple of hours, babies will magically appear within a few days. Just make sure to cover filter inlets with tights or use a sponge filter so they can't get sucked in.

Thanks Fishlady - my thoughts, also. I don't want to risk it and prefer established methods until I get assurance on the toxicity issue.

But I do wonder if this might present an easier option for domestic breeding for egg layers. Easy, clean and inexpensive. I do wonder if it is worth a try. (Incidentaly my text should have read "100% non-toxic" - not 100 non-toxic). Does anyone out there have have any hard evidence on poly acrylamide toxicity? Any polyacrylamide experts out there?
All comments welcome.

Please do not try using polyacrylamide as any presence of unpolymerised acrylamide could play havoc on the fish. It is a neurotoxin.

Also in dilute water it will degrade to produce ammonia.

Thanks Tknoxx
Very helpful. The stuff says 100% non-toxic on the pack, but that might be because its sold for plant use and in that respect the degradation you describe may indeed be non toxic to plants.
A nice idea then, but no cigar!

I have seen these just the other day,
My Daughter pulled it apart in under 10 seconds,
I would say no, just cos there is a chance the fish may try to eat them and they could easley come apart.

Thanks Critch
The consensus is to give it a wide berth - and indeed I will. The principle appears to be whether unpolymerised acrylamide exists and I have no way of knowing whether the polymer process is complete or whether residual unpolymerised acrylamide still exists. Also the eventual breakdown of the product is a concern (though it would probably be used for no more than 48 hours or so).
All in all, best avoided, I think.
Thanks again.

It says 100% nontoxic as itself is nontoxic. however there are residual levels of unpolymerised acrylamide left over after polymerisation, this level would be very low, but I still wouldn't risk it. Plants do not have nerves so a neurotoxin would not work on them and the ammonia produced would be absorbed by plants while as you know fish tanks should keep ammonia down at 0. I t was a nice idea but it's one that's just not going to work out. There are acrylamides in some starchy foods at low levels and there also may be a link to cancer but the low levels in the balls would be unlikely to affect a human.
You could try to get a big bag of marbles in a charity shop maybe?
Btw where do you get the polyacrylamide balls so cheap? Need some for plants as the soil can be very messy!

I did try for marbles but they are relatively expensive (and I've just been made redundant). Even our local charity shop check e-bay rates before pricing up their goods. I calculated that for a 16x10" temporary breeding tank I need over 400 (1.6cm dia) marbles for a single layer. Most written methods suggests at least two layers. On e-bay marbles are going for about £5 per 100.

The polyacrylamide balls were just £1.50 for 10g (about 5cc). They apparenyly absorb water to a ratio of 1:180-200. I got them at a local car boot sale in Essex. They are branded "Crystal Soil".

To widen the debate the manufactuer's website (http://www.crystalsoil.com/crystalsoil) states they are ".....a more convenient way to provide water to animals during transporation. The water soaked polymer crystals won’t spill and animals can eat them to get water". Given the comments about nervous systems its surprising this is permitted in the UK. In their FAQs is the following:
Q. Will Crystal Soil hurt my family or pets if they eat it?
A. No. It is 100% non-toxic and biodegradable.
I have contacted the manufacturer for their view and will post the reply here.
....Interesting, eh?

Do post their reply (or the gist of it) as it will be interesting to see what they say