Drop-offs, overhangs, and undercuts: Niches within the niches...and the art of "editing"

Niche habitats have always fascinated me. You know, distinct little areas within a larger habitat, which provide unique and different ecological and structural characteristics for the fishes which reside in them. 

The interesting thing about niches is just how fishes come to inhabit them.

Among the richest habitats for fishes in streams and rivers are so-called "drop-offs", in which the bottom contour takes a significant plunge and increase in depth. These are often caused by current over time, or even the accumulation of rocks and fallen trees, which "dam up" the stream a bit. (extra- you see this in Rift Lakes in Africa, too...right? Yeah.) 

Fishes are often found in drop offs in significant numbers, because these spots afford depth (which thwarts the hunting efforts those pesky birds), typically slower water movement, numerous "nooks and crannies" in which to forage, hide, or spawn, and a more restive "dining area" for fishes without strong currents. They are typically found near the base of tree roots...From an aquascaping perspective, replicating this aspect of the underwater habitat gives you a lot of cool opportunities.

And of course, these types of habitats are perfect subjects for aquarium representation, aren't they?

If you're saddled with one of those seemingly ridiculously deep tanks, a drop-off could be a perfect subject to replicate. And there are even commercially-made "drop-off" tanks now! Consider how a drop-off style encompasses a couple of different possible niches in the aquarium as it does in Nature!

Overhanging trees and other forms of vegetation are common in jungle/forest areas, as we've discussed many times. Fishes will tend to congregate under these plants for the dimmer lighting, "thermal protection", and food (insects and fruits/seeds) that fall off the trees and shrubs into the water. (allochthonous input- we've talked about that before a few times here!) And of course, if you're talking about a "leaf litter" or botanically-influenced aquascape, a rather dimly-lit, shallow tank could work out well.

And of course, in the areas prone to seasonal inundation, you'll often see trees and shrubs partially submerged, or with their branch or root structures projecting into the water. Imagine replicating THIS look in an aquarium. Contemplate the behavioral aspects in your fishes that such a feature will foster!

Lots of leaves, small pieces of wood, and seed pods on the substrtae- doing what they do- breaking down-would complete a cool look. For a cool overall scene, you could introduce some riparian plants to simulate the bank as well. A rich habitat with a LOT of opportunities for the creative 'scaper!

Why not create an analogous stream/river feature that is known as an "undercut?" Pretty much the perfect hiding spot for fishes in a stream or river, and undercuts occur where the currents have cut a little cave-like hole in the rock or substrate material near the shore.

Not only does this feature provide protection from birds and other above-water predators, it gives fishes "express access" to deeper water for feeding and escaping in-water predators!

Trees growing nearby add to the attractiveness of an undercut for a fish (for reasons we just talked about), so subdued lighting would be cool here. You can build up a significant undercut with lots of substrate, rocks, and some wood. Sure, you'd have some reduced water capacity, but the effect could be really cool.

Fun niches to consider for your next tank..or your existing one, too! I address this idea, because I get a lot of emails that read something like, "Damn, Scott I like that idea you just mentioned, but I can't get another tank, and my current one is established and I'd hate to break the whole thing down!"

There's no reason why you can't embrace one of these ideas and incorporate it into your existing aquarium, right? I mean, sure, you may have to do some "remodeling", but it's certainly do-able!

Yeah, you CAN revise your aquarium while it's "mid-life-cycle" and: a) not kill all of your fishes, and b) significantly alter the type of habitat that you're representing in your aquarium. 

Yeah, our fishes are a lot more resilient than we give them credit for!

I recall not too long ago, when I would work on my aquariums and needed/wanted to do something that would be sort of disruptive to the tank, like moving some rocks, wood, tearing out some plants, etc.- I literally had to "psych myself up to do it.."  I was always of this mindset of "Don't do THAT- it'll upset the whole system..."

I used to feel that the whole idea of keeping an aquarium was to keep it pristine and untouched, like the day it was set up...sort of like a new car...you know...don't get that first scratch on it! Like, I was afraid to do stuff that would stir up the sand or to move stuff around too much. I mean, I felt that this activity could disrupt the system to "the point of no return."

I was worried it would stress the fishes too much, or whatever.

As if Nature isn't a rather chaotic place, filled with all sorts of natural occurrences for which our fishes need to compensate for in some manner, right? Now, I realize that in Nature, a fish can escape pretty far away from a disturbance, but still..a disturbance is a disturbance, right?


Now, I realize that digging deep into a long-established sand bed or tearing out all of the long-established biological filter media in a highly populated tank are examples of "no fly zones"- stuff you'd be foolish to do- stuff that CAN have real negative consequences for our fishes. Disrupting the function of the biological filtration of your aquarium is always a sketchy prospect, at best. 

But stuff like moving some wood... repositioning rockwork, or just netting out some fishes temporarily while you do a major disruptive cleaning isn't all that bad...That kind of stuff would typically stress ME out far more than the fishes I'd be so worried about. And, in decades of working on tanks, I honestly think I could count the number of fishes lost during heavy-duty work in their tanks on the fingers of one hand...I mean, I can't really recall any incidents! I mean, for a LOT of fishes, it's just not as big a deal as I seem to have made it over the years...Really.

Sure, moving around fry or newly settled-out marine fish larvae, known delicate fishes like Discus, or disrupting fishes tending to their brood is an obvious "no-no", but let's be honest- moving 'em around periodically is not such a big deal.

Breeders and people with 50-tank fish rooms know this initmately!

I have no idea where this mindset/perception of "disruption=catastrophe" that I held for so many years came from. 

And, as I heard a little kid say once in the LFS to his dad, attempting to convince him to buy that Red Tailed Shark right then and there, while the father reminded him that they still had a day of shopping ahead, "Dad, fishes don't break so easily...."

Brilliant. Perfect, even.

I couldn't have phrased it any better! The little guy was spot-on!

I think that we, as hobbyists tend to get a bit nervous about "messing" with tanks in general.Yet, I can't help but think that a well-thought-out aquarium which embraces biological stability and common-sense aquarium practices can create a natural "line of defense" that will provide protection and foster resiliency in our fishes.

 So, yeah- if you have an urge to switch it up now and then, study your tank, think through the process, and execute...And be willing to accept some risk. 

Look at some of those unique niche habitats, and see how you might be able to incorporate them into your next tank...Or your existing one!

Stay thoughtful. Stay resourceful. Stay creative. Stay diligent...

And Stay Wet.


Scott Fellman

Tannin Aquatics 

Scott Fellman
Scott Fellman


Leave a comment