Backyard Aquaponics
A place to discuss aquaponics

A $55 one from eBay - uno board, Breadboard, and a bunch of sensors, resistors and connectors. Contemplating getting the yun (arduino board with built-in wifi), but I have a spare wireless router that I might use instead.

I'd just get the arduino alone. Then buy the parts that you need online or at Jaycar. You won't use the majority of the bits and pieces they send you. Far cheaper that way.

And with the wireless router, you're opening yourself up for a world of trouble. Connecting a spare wireless router to an existing service is a nightmare, and if you get it to work (which is very painful, and most routers won't go into a wireless bridging mode), it hogs and slows down everything else. It's the reason I don't have my live sensors up and running atm. Seriously, a nightmare, and very last resort.

The yun is easier, or get a raspberry pi, and hook a wifi dongle into it. Far easier. Although I don't know how to code python, C++ is as far as I've gone.

Just thinking out loud - maybe if the sensor was at the top of a slo-like pipe it might be less prone to false readings due to splashing, fish feeding of other things that disrupt the water level? Or maybe a rolling average would smooth out false spikes (if they are intermittent) ?

You're over thinking it.

The spikes are like a millisecond worth. Average out the readings on the arduino before sending them off, or even take the reading once a minute instead of every 50 milliseconds like I did. (I'm assuming you're going for an alert system).

Cool, will keep that in mind.