Nyagua is a little piece of software that may help you to manage your home aquarium. It can store data about measurements in aquariums and produce graphs from these. It can store data about expenses and produce a report with yearly, monthly, and daily costs. It reports the compatibility between fishes and plants in its database. It can import fishbase.org XML data, and your own pictures can be added.
PAFCalc (Planted Aquarium Fertilizers Calculator) for Android is a useful utility that helps in calculations related to DIY fertilizers for planted aquariums. It has been completely written with the Android developer studio, which should ensure portability to tablets and smartphones. The app doesn't access any external functions on your device.