More Pondage

Using solely the homemade box filter and the 110W UV-C steriliser, the pond is now almost crystal clear and I can actually see the bottom. It's a massive difference from the green miasma from just over a month ago where you couldn't see deeper than a couple of inches. 

However, it's so clear that I managed to see 8 small koi shoaling in the shallow end. I always thought Hay was spinning me a yarn when she swore she's seen 2, but she was right. Two of the 3 adults have managed to reproduce. I also saw one koi that was clearly a new resident, but about 6 inches in length, so that must have hatched last year and remained hidden in the green goo.

You can just see the tiddlers in this video:

Now a pond the size of ours can only support 7 or 8 adult koi (30cm each) that feed off whatever is in there, without adding fish food. We already have 3 that size and it will be a while before the rest get to that size, a couple of years probably, but a bit of culling will be required at some stage.

I may have to issue fishing licences to keep stock levels at a reasonable level, or introduce a pike. Medieval monks kept pike, trout, bream and carp in their fishponds to eat. Koi are not generally considered edible as they have a muddy taste, although if carp were considered edible, I can't see why anyone would balk at koi - they're the same family.

The box filter is no longer getting clogged with green algae and I've removed the fleece media, allowing the more porous stuff to take over and become colonised with beneficial bacteria. I've also bought some alfagrog, which is a pumice-like material that the beneficial bacteria can also colonise as the water runs over it. The stuff sounds like an alcoholic drink for The Hulk.

I may not even need to use the large filters I bought, but we have nevertheless taken the decision to build an 8 foot x 10 foot shed next to the pond to house whatever I do decide to use. It will also be a useful store for the various bikes we have scattered around the premises. This is the one we've ordered for arrival by the end of July. Colin, our tame builder and neighbour has been charged with making a suitable sized concrete pad and erecting the shed.

Hay wants to create some areas where she can grow watercress, which will require unfiltered water running through a gravel bed in which the watercress can thrive. The watercress roots will also assist in keeping the ecosystem sweet, obtaining nutrients from the unfiltered water, although that will require a separate pump from the filter pumps. Using filtered water would strip any nutrients from the water that the watercress roots would be in.

It's looking good, but there are still a lot of weeds around the pond that Hay has to cull. Not my job!