Let’s discuss where your RFA’s are in your tank, i.e. on the rocks, at the edge of a rock, in the sand or do you have some other location?
In the wild, the shallow water RFA’s that I see are almost always attached to rocks that have a hole. The nem sets its foot in the hole and can retract into the hole when disturbed or when ingesting food it has caught. Many of them are in holes on the vertical surface of the rock and away from the sand. But almost as many or in holes that are on horizontal surfaces and may have sand around them as well. Sometimes there is no sand, sometimes just a little sand and sometimes the sand is 2 or 3” deep.
The first time I tried to place a number of RFA’s on a flat rock, they all moved to the edge of the rock at the sand. Some even attached just under the bottom of the flat rock and reached up around the edge to be above the sand. However, I have seen a couple of photos of people’s tanks with RFA’s attached to rocks well up away from the sand. I assume these nems have their foot in a hole they like and are happy there as well.
What I’ve been doing most recently is buying various sizes of PVC end caps. Before I put a new RFA (or move one for some reason) I pick an end cap that is just a bit bigger in diameter inside than the RFA’s foot (yes, it’s a real guessing game). Then the PVC end cap and RFA go into a 16oz deli cup full of tank water. About 95% of the time, the nem settles down inside the PVC end cap and attaches. It may happen quickly, it may take a couple of days. Then I can take the PVC end cap and transfer it to the tank. I push the end cap down into the sand so that just a tiny bit of the end cap’s rim is exposed above the sand.
At this point I’ve never had a RFA move from the end cap. After a week or so, I’ll often go back and push the end cap down just a bit more so the rim disappears in the sand. At that point the sand will start to get inside the end cap with the nem. I have 10 of my bigger RFA’s in end caps now. The other 20+ RFA’s in my tank are loose and fending for themselves. Most of them fairly small and attached to the edges of rocks at the sand.
I like this way of keeping some of my RFA’s. It allows me to keep the bigger, more mature and possibly ready to mate nems close to each other for better potential spawning. It also makes it really easy to pull one out of the tank if I decide to sell one to a friend or customer who comes to my house and falls in love with them. And I have to admit, that does happen quite often! That visitors fall in love with them, not that I sell them… at least not until they’re about 2” in diameter.
Here is a photo where a couple of the RFA's are a bit retracted and you can see the PVC end caps.
20180622_144452 R1 by
Ron Lindensmith, on Flickr