Thanks for your reply, and I appreciate all the experimentation you've done with respect to Matrix and De*Nitrate. Perhaps I am barking up the wrong tree with a Matrix/De*Nitrate solution, it could be, but...
I see it as a three front war actually, Nitrogen Cycle, Silicates, and Phosphate levels. I theorize that silicates and phosphates may be just as responsible as the Nitrogen Cycle. I think these three issues have to be addressed to resolve the brown diatom issue.
The term "Brown Algae" is a misnomer. Brown Algae (Diatoms) are not Algae. I don't have any issue with actual algae whatsoever, which makes me think my lighting is under control, along with the fact that I've done considerable experimentation with my lighting to no avail. There's wide disagreement in the forums and online as to whether more or less lighting has any effect whatsoever on brown diatoms (brown algae). I've personally concluded that lighting really has little or no appreciable effect on their proliferation in the tank based on my own experimentation.
Brown Diatoms flourish from silicates being in the water, which with our hard water occurs every time I do a water change or top-off the tank, and silicates and phosphates accumulate every time you top off the tank. Brown Diatomes (Brown Algae) like phosphates (which is tap water related related), and they like Nitrates too. That's why I've been experimenting with Purigen and Phosguard, and want to improve the Nitrogen Cycle, in an effort to help reduce silicates, nitrates, and phosphates in the tank, which reduces the environment for brown diatoms to flourish.
I've been running a Deep Blue UV Sterilizer for the entire time that the brown diatoms have been a problem. UV Sterilizers will only help with parasites, and I do like having a UV sterilizer in the mix to reduce the potential for parasites in the water. But, brown diatoms aren't parasites, so I don't really expect the UV Sterilizer to help me much with brown diatoms.
I've had planted tanks in the past, and frankly, they can complicate this issue because you have to simultaneously worry about properly nourishing them, due to dosing nutrients and delivering proper lighting. So, for now, I've omitted plants so I can focus on the brown algae without having to simultaneously introduce another criteria to worry about, of having to properly nourish the plants without the balancing act of making sure I am not nourishing the brown algae (diatoms).
So, while I might still be barking up the wrong tree with Matrix and De*Nitrate, with lighting eliminated, plants not being an option for now, and UV already running in the tank, that leads me back to the Nitrogen Cycle, Silicates, and Phosphates.
So, my theory about the bio-wheel on the previous Penquin filter not doing it's job was my first lead into a conclusion that the Nitrogen Cycle is part of the issue, and the idea of adding plants also suggests that same avenue of thought.
So, the cheapest fix, if in fact the bio-wheel didn't help to establish an adequate bio-filter in the tank, is to change out the filter design by going to the Aquaclear filters, which I already have in my stash (cheap), and to add the Matrix to the Aquaclear 50 chamber (cheap), and also to experiment with De*Nitrate in the Aquaclear 30 chamber too (cheap), in an effort to establish a better functioning bio-filter.
Once the new bio-filter is established, and my test kit confirms that the cycle is mature, I plan to use Phosguard (cheap) to remove silicates when I do water changes and top-offs. I haven't decided yet whether, once the nitrogen cycle is established, to use Purigen to remove ammonia, nitrites, and nitrates. That might be the time to introduce some live plants instead, but only after I'm convinced I have the diatoms under control.
I am going to try your suggestion of a bio-sponge in one of the Aquaclear filters, probably the Aquaclear 30, where the De*Nitrate is also being housed right now as well. I've heard good things about using a bio-sponge, and your suggesting it reminded me to move forward with that.
Is there a particular brand of bio-sponge you've had the most success with and can recommend?
I've even started to research building a DIY Sulfur/Matrix Denitrator/Reactor Canister Filter. It's one of those DIY projects that are good for winter time. It's cheap to make too, and most parts are easy to get at Lowes, so why not play with it?
I think you're barking up the wrong tree. First, even a highly effective bio-filter will do little to combat algae of any kind. Matirx and DeNitrate will not help you. These are pumice stone products that promise to promote both aerobic and anaerobic bacteria to complete the N2 process by converting ammonia->nitrites->nitrates->nitrogen gas. This does not affect algae.
I used both (Matrix & DeNitrate) products for nearly 2 years to attempt to culture anaerobic bacteria to process nitrates into N2 gas. First, I added an additional AC70 filter with an AC30 impeller filled with a mix of Matrix and DeNitrate. Later, I 'invented' a filter that used a LOT of the media and lots of Stability with NO success. I was never able to reduce tank nitrates!
In the end, I find that bio-sponge is perhaps the best bio-media and culturing anaerobic bacteria in our highly oxygenated FW tanks is very difficult, if not impossible.
I'd suggest you invest in sufficient lighting to heavily plant your tank. Use bio-sponge material in your filter. For the brown algae or any free floating algae or diatoms, perhaps consider a UV sterilizer.