There's a Reason for Not Keeping Otocinclus with Altum Angels
Q. I recently purchased three altum angels, and they have been eating and doing very well in a 265-gallon planted community tank. Recently, I noticed one of them with its mouth stuck wide open. I then discovered that it had tried to swallow one of my Otocinclus catfish, which was still in its mouth! What can I do to get the catfish out of the angel's mouth? I tried to pull it out, but I didn't want to pull too hard because I know the Otocinclus has spines in the fins. Have you ever heard of angels eating Otocinclus? I have several regular angels, some much bigger than the wild altums, and they never seem to bother any of my Otocinclus or other smaller fish.
-- Anthony Biro

A. I'm not surprised that one of your altum angelfish (Pterophyllum altum) has tried to eat one of your Otocinclus catfish. With all the stories one hears about angelfish eating smaller tankmates, such as neon tetras (Paracheirodon innesi), it's to be expected that other small species like Otocinclus would also make the list of angelfish dietary supplements. So, to answer your second question first: Yes, it happens regularly.

Over the years, my experience with Pterophyllum has shown them to be very efficient and determined predators of other cichlid fry. Combined with their reputation for eating neon tetras, one can easily see that Pterophyllum are fish eaters — at least opportunistically — despite the popular notions of refinement and restraint bestowed upon them by their owners. I think your altum was simply trying to do what it would have done in the wild.

Extracting a spiny catfish from the mouth of an angelfish can be difficult, and unfortunately often results in the death of both fish. First, you need to assess the situation in terms of how far the altum got in swallowing the Otocinclus. If the pectoral and dorsal spines have locked in place and prevented the angelfish from getting it down very far, you may be able to gently wiggle the Otocinclus out.

It's likely, however, the fin spines will be stuck firmly in the sides and roof of the angel's mouth, so significant movement is simply not possible. If that's the case, then a surgical extraction is needed. A very small pair of scissors can be used to cut off the pectoral and dorsal spines of the Otocinclus so the catfish can be removed. Unfortunately, the procedure will probably result in the death of the catfish.

If you decide to go this route, remember to remove the spines from the altum's mouth before you release it back into the aquarium. The procedure will also be extremely stressful on the altum, so any effort to get the angelfish back in the water and keep the procedure as brief as possible will help the angel to recover. There is, of course, the chance that despite your best care the altum will succumb to the stress.

Hindsight — taking at least some advantage from this experience - should cause you to re-think the community of fish you have in the tank. I suggest replacing the Otocinclus with a larger species of algae eater to deter your angelfish from attempting to eat such a dangerous meal. There are larger Otocinclus occasionally available from specialty importers; research some of the alternatives and ask your local aquarium store to order some for you.

As your altum grow larger, your current Otocinclus will look increasingly smaller to them, making these little catfish even more tempting as a meal. I'd replace them with larger alternatives before another of your altums bites off more than it can chew!
-- Lee Newman

A Trial Separation
Q. Is a 10-gallon tank with a divider large enough to breed a pair of Melanochromis auratus?
-- Marcel Piltch

A. Melanochromis auratus are not large, so your 10-gallon tank can work. They are aggressive, though, and a small tank leaves little room for the female to escape the male's attention. The divider may prove essential to the female's safety.

Dividers have proven to be particularly useful for large, boisterous substrate spawners because they protect a female from an overly attentive male. Such dividers are often made of plastic "egg crate" (the material is used as a diffuser for fluorescent lighting and is available in the lighting section of hardware stores), which has holes that will facilitate spawning. The female can lay eggs on one side of the divider and the male is able to deliver his milt from the other side, fertilizing the eggs. Both parents are able to see each other, the pair bond is maintained, and when the fry hatch and become free-swimming, they can swim through the divider to either side of the tank and enjoy the protection of both parents.

Like many African cichlids, Melanochromis auratus are mouth-brooders, and they provide more of a challenge when attempting to breed them using a divider. For one thing, mouthbrooders interact more than substrate spawners. As the female deposits the eggs, the male swims alongside or behind and fertilizes them. The female then spins around, picks up the fertilized eggs and holds them in her mouth. This process is repeated many times.

If a suitable spawning site, such as a flat rock or slate, is placed so that it protrudes on both sides of the divider, mouthbrooding cichlids may be able to spawn while separated. If this isn't possible, there are other options.

If the female is smaller than the male a "partial divider" can be used. Cut holes into the divider that are large enough to allow the smaller female to pass through, but small enough to block the larger male. The female will have access to both sides of the tank, and the male will be confined to one side. If he becomes overly aggressive, the female can escape to her own side of the tank. When the pair is ready to spawn, the female can enter the male's side. After the spawning she can retreat back to her own side with a mouthful of eggs, to incubate them while free from harassment.

A different version of this method is to use an upturned flowerpot with a hole cut in the side instead of a divider. The hole should be small enough to allow only the female inside the pot.

If both adults are the same size, keep the divider in place while you condition the pair for spawning. After a few weeks of conditioning, select a day when you are able to keep an eye on the fish, and remove the divider in the morning to allow the fish to interact. There will likely be some aggression between the two initially, so be sure it doesn't get out of hand.

If the female begins to take a beating, replace the divider and condition the pair for a longer period. On the other hand, you may observe them as they spawn. If spawning occurs, be ready to replace the divider and isolate the female once she begins resisting the male's advances. She will then need time to incubate and raise her babies, and to eat and condition herself before further interaction with the male.
-- Craig Morfitt