From African waters come the Synodontis catfish, members of the Mochokidae family, a family of very 'catfish-like' fish. Many, many of them are attractively colored, and many have the quaint habit of swimming inverted, though some species do it far more than others. All make good community tank fish, though some grow large enough to be a danger to tiny fish. All are adaptable to pH and hardness levels, but of course they do have a preference toward their natural waters.
In this post I'll stick to riverine and lake fish, as I've not kept those species that live in the hard, alkaline waters of the African Rift Lakes.
Thus, most of them prefer water around neutral in PH, moderately soft to moderately hard. Though several of them don't come from plant-choked waterways, all of them, to my experience, deeply enjoy living in very well planted aquariums with driftwood and stones. All those I've kept in them have had deeper colors and more vitality than those I've kept in tanks with plastic plants and faux driftwood. I assume there's more food sources in planted tanks, like micro-crustaceans, that they eat, that improves the color and health so.
All of them are quite long-lived, as 20 years or more are not unusual.
You'll forgive me if I start the species list with my two favorites.

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Hailing from the Congo River, as do many in this list, is our first species - Synodontis angelicus - the Polka-Dot Catfish.
This is one beautiful catfish for your soft water, acidic tank, with pH 6.5 to 6.8 ideal. Upon maturity in such tanks, the keeper is rewarded with a deep, velvety purple fish covered with small, bright white or in some populations, yellow, spots, and the color is repeated in bands on the tail, dorsal fin and strong lead rays of the pectoral fins. Like all Synodontis, the Polka-Dot Cat has a long pair of barbels on the corners of its mouth, and two more feathered barbels on its chin.
Perfectly peaceful, given a place where it can retire. S. angelicus does reach 8 inches, so tankmates like larger tetras are the rule.
Kept with Congo Tetras in a large tank, say over 75 gallons, S. angelicus feels right at home. In large enough tanks, say 100 gallons or better, you can keep your angelicus in groups, as long as there are sufficient hiding places for all.
With enough hiding places, there will be no squabbling, and you may be one of the few to have your angelicus breed in your tank. They are egg scatterers among the plants. The single time they did so in my tank I was able to salvage enough eggs to raise 18 youngsters. To this day I don't know what triggered the breeding.
Best growth and color in this fish is from good frozen and live food. They like insect larvae, plant debris and shrimp. Frozen Mysis, mosquito larvae and bloodworms are happily eaten. A high-quality pellet can be staple, but to get good growth, feed frozen foods several times a week.
This species very occasionally swims upside down, usually either hanging under driftwood, or combing under plant leaves for tidbits. Other than running their whiskers along the leaves, I've never had S. angelicus or any Synodontis for that matter, nibble or eat live plants. Just so, a plant-based pellet may scratch their itch for plant debris.
The first Synodontis species I kept, and perhaps my very favorite of the family.

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Called Pajama Catfish in the trade, and another true beauty, is Synodontis flavitaenitus, of the Eala watershed in Zaire.
Rather shy and retiring at times, the Pajama Catfish sports a chocolate brown body with rich yellow stripes. The strong rays of the dorsal and pectoral fins are also yellow, and dark irregular stripes are all fins.
This species often rests inverted.
Reaching 8 inches long, S. flavitaenitus measurably deepens its color in planted aquaria with a dark substrate and with driftwood, coupled with good feeding.
Sexes are easily told, as he's slimmer, slightly smaller, and deeper colored than his mate. They really do improve when frozen and live foods are a large part of their diet; perhaps 50 percent. Quality pellets from various manufactures can make up the other half. Like most if not all Synodontis, Pajama Cats thrive best when fed insect larvae and small crustaceans, like Gammarius species shrimp, coupled with greens, like algae or plant debris.
This fish hides a bit more than the former, but that may be because I kept it alone. When I purchased this species, they were very expensive, even more so than angelicus. A cursory glance though the internet revealed Pajama cats still aren't to be considered cheap. An affable species, and quite attractive in health.
To my knowledge they've not been bred in home aquariums, though it's one species that is worth developing a methodology for, due to its looks. It would be a quite popular catfish were it available as captive bred specimens.

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Almost cylindrical in body is Synodontis bricardi, another catfish from Zaire, this time from the stone-strewn rapids at Kinsuka.
This catfish is another that does best in the soft, slightly acidic planted tank. Smaller than the former two species at a bit over 5 inches, bricardi really needs calm, non-aggressive tank mates, as it is easily intimidated and hurt. Rasboras would be ideal. Mid-70's in temps do them very well.
Since it does come from flowing streams, a bit of current in the tank would not be amiss. Don't let the dissolved Oxygen level dip below 8 mg/l with these fish. If the aquarium isn't well planted, air stones should be employed to keep dissolved Oxygen levels high.
The fish's long, cylindrically-shaped body is banded with wide, purple-brown bands and thin whitish ones. Bands of color are on all fins. Though the colors are modest, the effect in person is quite pleasing. A very attractive fish in health.
In feeding they are easily satisfied. Frozen insect larvae, shrimp and quality pellets should be staple, though they do appreciate variety in their diet. They DO need vegetation, so stock up on cucumber, zucchini and leafy vegetables for your catfish. Soon as they are discovered, bricardi will nibble at them until they are gone.
Blanching the zucchini is helpful, as it smashing the leaf spinach, etc. so the leaf flesh is visible.
Properly fed and kept, this fish is quite hardy. A charming species; recommended.
I kept them in groups with no problems. Mine never swam inverted in the years I kept the species.
As above, several hiding places to retire to at night are very helpful.
I know of no captive breeding of this species. They aren't as common in shops as they once were.

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The de facto leader in sales of Synodontis species is S. nigriventris - the Upside Down Catfish of the Stanley Pool in the Democratic Republic of the Congo.
Strongly nocturnal in habit, S. nigriventris spends the vast majority of its time inverted, which is an adaptation to eating insect larvae off the surface of the water at night.
Upside Down Cats are a species that deeply enjoys the company of it's fellows, and the more you have the more you'll enjoy them, and the better off your catfish will be. Since they are a smaller species, topping out at under 4 inches, eight in 55 gallon aquarium wouldn't be too many. Using a floating pellet as staple will allow you to observe natural feeding behavior. Floating pelleted foods are indeed best, but frozen food like mosquito larvae and Mysid shrimp will help mimic natural diet. They also should have a good vegetative pellet in their diet for optimum health.

To Part 2