How did you cycle these tanks?
What is the catfish species?
For a 4-foot I have...
1x Hypoptoma spp. catfish (needs chilled out tankmates when it comes to food, can easily be outcompeted)
1x Panda Garra
5x Pangio doriae (Eel Loaches, very peaceful, very delicate nocturnal loaches, work well with Hypoptopoma)
Numerous Ilyodon xantusi youngsters (a bigger goodeid member, like vultures at feeding time)
Numerous Lionhead Cichlid (Steatocranus casuarius) youngsters, need a good current, which might not suit Guppies
1x female Golden Wonder Killifish, but she would treat anything that could fit in her mouth as "live lunch" (so at least any new livebearer fry), albeit she is only a fraction over 6cm right now