I had retics for about a year and a half and they are a very fun little ray but if you dont have patience and the money to buy a replacement if one sudenly stops eating, dont get retics.
They normally will only eat blackworms and grow extremely slowly. If you want pups the rays wont be ready for almost 5 years and rarely live that long because of how sensitive they are. I'm not trying to discourage you, just want you to make sure you know what you are getting yourself into.
I would get a heavy filtration system, but you dont need to go crazy. Mine have made allot less of a mess than my bigger rays (marble motoro, leo, hybrid). For the 150 an fx6 and a smaller canister or HOB as a backup should work well. A big sump and an fx6 should be more than enough on the 400 for just a pair of retics.
Now, you gotta feed them, allot! I recommend smaller meals 2-3 times a day but I know that can be hard with work/school. I fed mine blackworms because thats all they would eat. They are very very picky. I've seen people get them to eat tilapia or pellets which are better.
Retics are big fans of burying themselves in the sand. I kept mine on poolfilter sand and they loved it. Play sand will also work but it'll get blown into the water column very easily and might clog your filters. Put in some clay pots and driftwood for some cover. Make sure the wood isnt sharp in any places. Retics have very sensitive stomaches and one of mine was a big fan of swimming on top of the wood.
If you want to get tankmates, theres a wide range of options. Im sure many people wouldnt do this but i kept mine with big peaceful-ish cichlids, a giant gourami, some catfish (rtc, sun, pictus), and I had a gar at one point. The cichlids include 2 huge Lyonsi, some oscars, and a jag. A safer option would be some geos, silver dollars, or an arrowana. You can also go the small tankmate route which works great with retics because of their small mouths. Fish like rainbowfish, tetras, and anglefish are great tankmates, even though one might go missing every now and again. Stay away from cory cats! I kept my female with some cories and they chewed up her tail causing her to get stressed and stay in the sand 247.
Good luck!
