They can also be obtained from quality LR/established ls from a fellow reffers DSB/or from the crud/rubble off the bottom of tanks used to cure LR.
A few sites sell them but in my opinion they can be obtained cheaper through the above sources.
LR is the best source but you can also buy kits from some websites.
<a href="http://www.ipsf.com" target="_blank">www.ipsf.com</a>
<a href="http://www.inlandaquatics.com" target="_blank">www.inlandaquatics.com</a>
