Progress on the Mark 4

The habitat with ballast containers and finalized layout:

A demo of the LED light fixture with the small USB battery I will be using for backup in case of temporary power failure (the air pump also has battery backup, but 14 hours of it. The LED lights will run for maybe 4 or 5 hours on battery. Both backups recharge for next time once mains power is restored)

Well, ballasting just got a whole lot easier.

Holy cow. I really really wish I had known this from the start. The problem of weighing these powerfully buoyant, air filled habitats down so they don't float has been, surprisingly, one of the biggest design challenges. What type of weight? How to attach it? Up until now I've been MacGuyvering ballast platforms from exercise weights bolted to wooden planks, concrete blocks, jars full of fishing weights and so on. But look at this. Look at the beautiful simplicity of it. This waterproof dry case is exactly the right size to contain two five pound diver's weights. Exactly.

As if that weren't enough, it has the exact same footprint as the deeper, transparent container used for the Mk.2 habitat enclosure because it's from the same product line. If you wanted you could just buy this slim case, the deeper transparent one, bolt them together, add weights, and you'd have done most of the hard work in building a habitat. My mind is blown at how much simpler this makes everything. Two of these, fully loaded, will total 20 pounds. Ample weight to keep the Mk. IV submerged and two of them side by side will neatly bolt to the floor of the enclosure with nothing sticking out or shifting around as you move it. No more shoddy fishing weight jars, or exercise weights screwed to wooden planks. Ballast can now be done in a tidy, attractive, polished manner that doesn't allow water to corrode the weights or lead from the weights to get into the water. And it consists of two products easily purchased online. If you're building your own, now you know. I just really wish I had discovered this earlier. Also I now have a waterproof digital camera good down to 10 feet that shoots high def video. No more wedging cameras inside the habitat, I can shoot video from outside even if it's in a lake or something.