This Stack Overflow thread offers both common methods of installation. I used the top voted one (below) but there is a full installation method in the thread.
sudo add-apt-repository ppa:ytvwld/asciiquarium
sudo apt-get update && sudo apt-get install asciiquarium
asciiquarium
The github page provides some requirements and installation instructions. Below is a summary of how to install.
git clone https://github.com/pipeseroni/pipes.sh.git
cd pipes.sh
sudo make install
pipes.sh
My favorite way to run pipes.sh is pipes.sh -t 7 -f 50 -R. That is pipe type 7 with framerate 50 and randomized start position/direction.
Cmatrix can be installed with sudo apt install cmatrix.
cmatrix
Using -s (screensaver) will make it exit on a keypress and -r (rainbow) will make the text appear multicolored.
In order to go full screen on the Raspberry Pi with Raspbian, I've been using xterm. I was only running asciiquarium but it becomes laggy after running for so long. My solution was to make a loop to start and restart the program. Then I thought Why not run a random program so I can have the joy of every screen saver. So I spent way too much time coming up with this command which loops forever and runs a random screen saver every hour.
while ((1)); do timeout 3600s $(printf 'xterm -fa monaco -fullscreen -e "asciiquarium"\nxterm -fa dejavu -fs 20 -fullscreen -e "cmatrix"\nxterm -fullscreen -fa dejavu -e "pipes.sh"' | shuf -n 1); done