I have been messing with filters for ages. It started with using large sewage pipes to hold filter media, and advanced to multiple stage filters that very effectively would do biological and mechanical filtration. I have constantly adjusted and improved on these, either to make them more effective, more practical, nicer to look at or safer.
My latest setup seemed to merge all of my experiences gained into one, or rather two filters. I had emptied my large tank, as I wanted to restart it from scratch. As it was already empty, I thought that I could as well make the orange PVC sewage pipe filter a bit more attractive and easier to clean. A lot of casual thought had gone into this, and the final result seemed promising. I am more of a hands on type. I don’t have any scientific approach to this, so I simply made the filter and hoped for the best. I knew that I couldn’t make the filter too big, so the only risk was, that they’d be too small or not effective.
This is the idea behind the filter. Water would enter through two large sponges on either side, move freely to the bottom of the filter and be sucked out from the top, forcing it to go through a layer of (bagged) ceramic filter media
Bellow are some pictures of the filter, while I was putting it together, and after it was established. I decided to do a “post filter process” to add an extra layer of filtration and a way to add carbon and phosguard.
The main idea behind it was, to let the pumps move water the shortest possible distance, in order to minimize their efficiency. Here, they simply move water over the edge of the filter. I wanted to avoid pushing water through long pipes, as that ads resistance and lowers the water flow rate. Gravity takes care of the rest. Water entering the system, moving towards the bottom and upwards towards the pumps is all down to gravity.
An other thought that I wanted to implement was, to let water go through as much filtration as possible at a reasonable rate. Not too fast but also not too slow. The reason is that I want the bacteria in the filter to be able to work on the water going through it, but still have access to new aerated water, so that they can keep functioning. My next step would be to add an air stone beneath the center filter media, to see if that improved filtration.
In practice, this worked really well! It kept ammonia and nitrites basically at 0 at any time! I was slightly disappointment at the sponges not being able to collect solid waste. They were simply too large to create any suction. The water went through them so gently that waste did not stick to them. I tried experimenting with adding barriers behind the sponges to gather the entry points into smaller areas. This did help, and I was looking forward to improving and tinkering with that.
But then it all fell apart
I have really not needed to do many water changes in my tank. Nitrates did build up, but not at any alarming rate. I mostly do smaller (20%-30%) water changes every 10 days to lower nitrates and replenish minerals. It is approximately 6 weeks into testing the new filters and as I did a water change yesterday, I wanted to check on the sponges. They were not too dirty and surprisingly, the dirt was on the sides of the sponges, which indicate that the water was trying to sneak around them. This was also an area that I was ready to experiment with but when I tried inserting the sponges back in, the whole filter gave.
It turns out that silicone does not stick very well onto acrylics. I had actually experienced this previously, when I tried gluing PLA to the PVC sewage pipes, but I had hopped that Acrylics and glass would stick better.
The good news is, that I run multiple filters, so it is not as catastrophic as it may sound. I have 3 internals filters by Aquael, and one more of my DIY filters, that I could simply move the filter media and pumps over to.
The bad news, is that the extra DIY filter that I have, also is made the same way, so it too will fall apart soon. I have to come up with a new design soon, that does not require me to empty the tank
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