If they haven't shown up and everything else is ok you probably havent havent introduced any. Do you have live rock or sand? usually a small piece of rock from the lfs will add some life. Be carefull if you have fish because uncured rock can have pests/diesease. If you have a friendly fish friend or store add a cup of sand from an established tank. that will def do it!
Most often copepods will come as hitchhikers on live rock or in live sand. Do you have any LR or LS? If not, getting the copepods may only be half the dilema. The rock and sand are the pods habitat, I'm not sure if a population would hold without much LR.
I do have a nice big piece of live rock, and have had it for about two months now, but I still don't see any. I have seen live sand for sale, I will have to check it out again this weekend, thanks for your advice everyone!
I have like 30 lbs of LR and like 25lbs LS in my 20 gallon but I think my Sally lightfoot and coral banded shrimp eat all my copepods...haven't seen any in months
my pods are so small i have to use a manifying glass to see the little buggers. With that and a a flaxhlight at night I still can't make out the whole shape of them. Look real close.
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You can never have too many friends.
You can help the pods reproduce by creating little rubble piles in your tank, out of rubble rock or empty snail shells. You can also purchase detritivore kits from, for example, Inland Aquatics