Funny, my little piece on "mulm" yesterday seemed to have provoked some good discussion, questions, and some thoughts amount various hobbyists, and a number of the discussions and questions seemed to focus on how we reconcile the use of substrate "enhancement media" (such as "Fundo Tropical", "Substrato Fino", "MLM", etc. with regular maintenance tasks, like siphoning the substrate.
As always, I defer to my own practices when answering these questions and offering an opinion, and I'll share my thoughts on the topic based on what I do and believe.
In my opinion, it is not a bad idea to siphon from the lower levels of the aquarium, without necessarily intruding into the bottom layers. On the other hand, many bottom-dwelling fishes like Plecos, Kuhlis, other loaches, Corys, gobies, and small cichlids tend to disturb the bottom layer for you, (the extent depending upon what type of fish, of course) right? Even some snails (I experience this regularly with my Nerites snails I keep in my botanical-style brackish tank regularly) will disturb the upper substrate layers to some extent.
I personally am not a big fan of siphoning into the substrate- haven't really done this for years, being a reef aquarist type, not wanting to disturb the substrate. I tend to change water weekly (10%-20% of tank volume typically), and have never experienced any issues. Your continued overall good husbandry (good stocking levels, careful feeding, and those water changes) should do the trick, in my experience over the years.
I'm of the opinion that decomposing materials act as a sort of "mulch" in the tank. Great for plants, obviously- but also good for fostering biological activity and encouraging the growth of microscopic life forms and perhaps even small crustaceans (like "Scuds" , worms, Gammarus, etc.) if you encourage them. To some extent, this is a sort of "refugium" mindset I have developed over the decades as a reefer- this desire to foster beneficial biological activity for the good of the aquarium in undisturbed areas of the tank.
I know "conventional aquarium wisdom" has for decades suggested that you want to siphon "detritus", uneaten food, and fish waste out of the substrate. I realize that for the vast majority of the aquarium world, this is a pretty good idea. I mean, why accumulate organic materials in the aquarium, which can impact overall water quality, right?
Of course, we are not the typical types of hobbyists to which this "wisdom" always applies. I mean, we allow leaves and botanical materials to decompose in our tanks. In fact, we encourage it. And further, we actually add crumbled leaves and finely "minced" botanical materials to accumulate in our tanks!
Yeah, it's a bit different.
I personally have always found natural aquatic ecosystems fascinating- particularly the substrates, be they comprised of sand, gravels, mud, etc. We've written about this topic from various angles over the years in this column. The substrates have profound influence on the water chemistry and biological activity/diversity of our aquariums, just like they do in nature.
So to me, the substrate represents more than just "bottom decoration", and as such, it plays a very important role on our systems. It represents a place for positive biological activity which supports the overall function of the aquarium. It creates an environment and setting that, while aesthetically different than what we have been "raised" to believe as "normal" in the aquarium world, when properly managed, sets the stage for a more natural appearing and functioning closed aquatic ecosystem.
I have never felt it necessary to dig deeply into the substrate in order to keep the aquarium "clean." Personally, I think that denitrification and other biological processes occur in bottom layers...and there has been some research in the marine aquarium world that it occurs in very shallow regions, too- and that almost any probing into a substrate disturbs these processes. Now, my conditions are that you don't have a substrate that's turned into "concrete", impervious to any water movement, that's another story. There should be some interaction between the overall aquatic environment and the substrate.
That being said, if you want, I suppose that you can disturb the surface layer by stirring, then siphoning up any uneaten food or fish waste right from the water column. I mean, you COULD siphon the substrate directly, but you'll end up both disturbing some of the very biological processes we're trying to foster, as well as taking out the substrate materials over time (thus necessitating replacement). Obviously, if you have live plants you wouldn't likely disturb the substrate (much like in "dirted" planted aquariums.), right?
Kind of my thinking here.
Oh, and I use good circulation in my tanks, as I think we all should. It's a sort of fundamental part of husbandry.
I mean, I could go round and round on this topic, because there is truly no "right" or "wrong" way, but the reality is that I tend to minimally disturb the substrate in my tanks, regardless of composition. I've never experienced any issues of any sort in my aquariums with this practice. Again, I am a fanatical frequent water-change guy, a careful feeder, and don't overstock my tanks.
I think it all boils down to husbandry. And it starts from the bottom...
And of course, a degree of acceptance of a different sort of aesthetic. You know...decomposing leaves, botanicals...stuff like that!
Stay bold. Stay committed. Stay curious. Stay open-minded. Stay experimental...
And Stay Wet.
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