Might have to seperate them, he's probably not up for that health wise, though mentally he's obviously quite confidant in himself.
She might be sensing theres something wrong with him, and isnt about to let him just become her mate again without a lot of testing, which he probably would fail. Might just be that he's passing his peak, not all or even most cichlids pair for life, a lot of them ditch a partner as soon as they think they deserve something better or stronger. female fish are very choosy and often more able to tell when something is wrong with a partner than we humans are. Ive certainly seen reintroductions after seperations go better than that. Often a scuffle, but that one was prolongued and intense. I dont think she wants him as he is at all. He's failing the strength tests she is obviously demanding, under normal circumstances the male is tougher and she would be able to do that to him.
If you want to keep him going you'll need a bigger or at least deeper QT. He probably wont fade without a partner, but it might be that your QT conditions arent quite good enough for him to regain fitness. I'd consider retiring him from a partnership. Have a feeling he regards her as his, but she wont accept that and he will take a lot of beatings.
Fish looks of good weight, yet appears anaemic, with some of the coloration you'd associate with hypoxia. There is obviously a bit of light blanching going on, its in night colours obviously, probably due to not being in its usual brighter tank, but it still doesnt look quite right. Sort of paunchy.
Curious, last thing I saw with that sort of symptomology were rift cichlids with Trypanoplasma protozoan infections of the the bloodstream, though cryptobia strains can give a similar appearance, but I assume they would have wiped out more fish if they were present, and no reason to assume hexamitiasis, the symptomology doesnt seem to be consistant enough for that, and whirling disease would look more pronounced by now, in term s of colouration its both too pallid and to structurally well composed to be that, as if it had it, it would surely be worsening badly by now.
Any reason to believe this might have been a wild caught fish or that it may have suffered ectoparasites like leeches or fish lice at some point?
I'm just thinking Trypanoplasma protozoa would be one of the longer term infections. Its actually more common than people realise in rifts, some fish have high resistance to the parasitic burden at least until it starts hitting the renal system, doesnt tend to wipe out all fish in the tank, basically because its transmitted by bloodsucking ectoparasites and victims might last months, potentially even years without full symptoms.
Might be worth a go with triple sulfa treatment before putting the fish back in community, see if it gives it a lift, or at least puts his symptoms genie back in the box for a few months or years. I dont think there is a real cure if i'm right about what it is. Given the low likelihood of transmission though, it could probably be worked with.
You can just WC melafix out, when it degrades its not toxic or a massive food chain toxin like dyes and formalins can be. It will eventually decompose perhaps pushing nitrate up a little but with sensible water changes you'll never notice.
On the lenses people do like the shot quality from the tamrons, the glass is pretty good but the barrels for zooms and focusing do feel cheap and nasty, the guarantee might be longer but you'll probably need it, on the nikon you probably wont and it will be smoother to use. I had the option to go for a tamron lens when I bought the camera for an extra 50 quid, but I declined and picked up a canon one for a hundred instead. My focus hitrate in tricky light is a little better than if i'd gone for the tamron as a consequence. The nice people at london camera exchange let me try them out back to back so I could get a feel for them. If I was going for the non camera brand lenses it would probably be sigma all the way.
POMV regulated med, needs to be got from a vet, though I believe people have found it on the net before now. Usually a liquid suspension if intended for use with aquaria, though tablets will do as long as they are water soluble, which is something you have to check as oddly enough many of the tablets arent, they need digestive juices to dissolve them. In the states they do medicated feed with it in too.
Spent yesterday mucking around with filters, my polariser was rubbish cos its a linear one, but oddly enough the UV filter which my camera isnt even supposed to need seemed to do nice things with colour tones and reduce any purple fringing in bright sunlight.