What pikes are you lookin on keeping? Large and aggressive? Colorful, flashy pikes? Bold, robust ones? Slim and slender, more 'passive' pikes? There are so many species available with so many different personalities and sizes its not even funny. How about you look at a few pikes from a few of the families and you can decide which way you wanna go.
Dwarf pikes: Crenicichla compressiceps, and Crenicichla regani are two of the more common species available. These pikes rarely get any larger than 5" total length. Not really bruisers size wise, although their attitude can make up for it quickly. Generally they are more conspecific than their larger counterparts. In other words, they don't really like other pikes (most pikes are this way), so its best to start out with a larger group of them, and allow them to pair up. Once they have paired up you have to remove the other pikes if you want them to live. Or you can just keep them singly. In a larger tank, you MIGHT be able to get away with more than one pair, but dwarfs are generally more aggressive then most Crenicichla, so it might not work. They are gorgeous fish, and can actually be kept in community tanks that their larger 'cousins' don't do so hot in. Min. tank size for a pair of dwarfs would be 30gal. Any smaller than that and you will start having problems most likely. A single dwarf could be kept in as little as a 20gal, although bigger is ALWAYS better!!
Saxatilis: Crenicichla sveni, Crenicichla lucius, and Crenicichla anthurus are some of the more 'common' Saxatilis pikes. They are quite a good bit bigger than the dwarfs, but not the largest pikes available. Get around the 10 to 12" range, and are rather thick. Are really gorgeous pikes, with their own unique personalities. What you see is what you get, for the most part! They will color up with age, and in some species its pretty dramatic. As with all pikes, its best to get a group of them if you want more than one, and allow them to pair up naturally. A 75gal is the min. for a pair, and a 55gal for a single pike.
Lugubris: Crenicichla sp. 'xingu I', Crenicichla sp. 'venezuela', Crenicichla johanna, Crenicichla marmorata, and Crenicichla lenticulata are some of the regularly seen Lugubris pikes seen for sale. These are the bruisers, gettin up to 24" (sp. 'venezuela'...although I've never seen one that large). Normally they range from 12" to 18" depending on the species. They are very robust, and some species can be quite aggressive. You have to choose your tankmates wisely with these guys, as they can easily kill, or eat a lot of fish. This is my fav. group, as they are so diverse and beautiful. The best part is the color changes. As they mature, they go through a series of color changes. In some species its dramatic, and you almost wonder if they are the same fish. Definately a treat to keep. 100gal is the minimum for a pair, and 75gal is the minimum for a single pike (adult).
As for feeding, its really simple. Meaty, protein rich foods like mysis shrimp, krill, cocktail shrimp, catfish nuggets, earthworms, sinkin carnivour pellets, black worms, and even algae wafers are taken. Basically any food you put in your tank your pikes are gonna eat. You might have to train them to eat certain foods, but with patience almost any pike can be taught to eat almost any kind of food.
Water conditions aren't really all that important as long as you avoid the extremes. If you are wanting to breed them though, soft, acidic water is definately a helpful thingyer. Hope that helps yaz a little bit! If you have any more questions please follow through with them!!