Effects of live sand & mud on the microbial communities in my tanks (updated with new data)

[Juano908]

I just ordered some mud to seed my new AIO Fusion 15 now my question is: how should I add it to the tank, since this is AIO tank and no sump?
Thanks a lot in advance.

Any ideas?

 

[Gregg @ ADP]

[updated Feb 17, 2020 to include data from an additional tank]

One of the most common questions I get is "If there's something I don't like about my aquarium's microbiome, what can I do about it?" In this thread I'll describe my experience with this question on my own home tanks.

The punchline is this: my experience suggests that live sand and mud provide a very low-cost way to adjust the microbial communities in established reef tanks.

Since this describes my home display tanks, which differ from each other in several ways, this is more of an anecdote than a formal experiment. But I figured since it provides a realistic example of what a hobbyist can do with this in a real world setting, it would be worth sharing anyway. (I'll update the thread in the future as I continue to monitor the communities in these tanks)

What I didn't like in my initial tests
The microbial communities in several of my home display tanks were not as diverse as I wanted, and were dominated by different bacterial families than the typical pattern I'd seen in healthy reef tanks. I wanted to change that.

I have four systems in my home (each includes 2 or more tanks so I count by systems instead of tanks). Three of them showed communities dominated by Alteromonadaceae. This was a pattern I've seen in many tanks I've sampled. It's one of the most common ways for a tank to deviate from the "typical" community (i.e., the average of healthy reef tanks I've sampled) -- a bloom of Alteromonadaceae. I don't have evidence showing this group causes a problem. I just know it's a difference from the community I wanted in most of my tanks.

Except Tank B. It has the highest levels of Alteromonadaceae. But it is also an unusual tank that is finally behaving like I want it to, after much work. Its unusual (among my systems) because it has no macroalgal refugium. Instead, I have lots of macroalgae in the display. Its mostly Gracilaria hayi with some other assorted reds, I'm terrible at algal ID. The tank is macroalgae, soft corals, and fish. Most of the display tank has low to moderate light and low to moderate flow... I call it the lagoon tank (Tank B, here).

I used to struggle with cyano problems in Tank B, which after a month or two of nitrate dosing to 5 ppm finally went away. Since then I've monitored nitrates and dosed as needed to maintain 5-10 ppm. Whatever microbial community is growing in that algal lagoon is working. I didn't want to disturb it, so I made that tank one of the controls, and didn't change anything.

I decided to experiment with the microbial communities in the other two tanks (A and D) to see how I could adjust them to make them more like the typical reef tank profile. I wanted higher diversity, less Alteromonadaceae, and more Pelagibacteracea and Flavobacteriaceae. Consider it purely personal preference, since they are my personal tanks. And I deliberately didnt change the other two systems, to serve as controls.

What I added to the tanks
For a variety of reasons I wanted to experiment with low-cost options for these tanks. 1) I'm naturally a cheapskate / bargain hunter in just about all aspects of life. 2) especially when it comes to optional expenses for a hobby. 3) when I've advocated live rock others have rightly ask, "this stuff is expensive -- aren't there any cheaper options?"

Here is what I found: live mud and sand at FloridaPets.com, collected in the Florida Keys. Please note I am not affiliated with this product in any way other than as a happy customer. I'm sure there are plenty of other suppliers, and I haven't done any kind of comparison between sources. It would be very interesting to compare sources... I am sure they all have different collection sites.

I bought 1 cup of the Live Keys Sand and 1 cup of the Live Mud for a grand total of $12.99. The material was shipped USPS Priority and looked and smelled good on arrival. I mean, the mud smelled like typical marine mud, but a normal smell, not a nasty decaying smell. I'm sorry I don't have a vocabulary like wine tasters' to describe this. I've just spent a lot of time around marine mud and the material looked and smelled reassuringly like normal ocean-smelling mud and sand. So in it went.

I split it in half, and added half to each of two tanks. I added it to the drain chamber of my sumps, which flows downward, providing the best chance of letting it settle out instead of blowing around the tank. I lowered it under the water surface to the bottom in a little tupperware container, then emptied the mud and sand into the chamber gently, to minimize mixing. That was it. Took about 5 minutes total. It created a little cloudiness when I added it that night, which was cleared up by morning.

Changes I observed in the tanks' microbiomes

I tested the tanks again about a week and a half after adding the sand and mud. The treated tanks initially ranged from low-diversity to very low diversity. After the addition of live sand & mud, these tanks ranked among the most diverse of tank I've sampled so far.

Treatment (Tank name)	Diversity Before (Percentile)	Diversity After (Percentile)
Control (Tank B)	151 (0.06)	360 (0.57)
Control (Tank C)	156 (0.08)	332 (0.47)
+Mud (Tank A)	201 (0.15)	544 (0.88)
+Mud (Tank D)	72 (0.00)	576 (0.92)

[edit: I've re-analyzed all samples so that the percentiles are calculated relative to the current database. A careful reader may notice that some percentile values have changed as a result.]



However, the untreated tanks also showed a smaller increase in diversity, showing typical diversity in the later sample. This remained well below the high diversity levels of the +Mud tanks.

Since I transfer small amounts of water between tanks daily during feeding, I speculate that this increase in diversity in the control tank may reflect transfer from +Mud tanks (remember, I treated this one like a hobby rather than an experiment. My tank habits predate my interest in aquarium microbiology!)

The changes in communities were even more striking. The systems treated with live sand & live mud had obvious reductions in Alteromonadaceae. Both of them also showed increased levels of Pelagibacteraceae, and Tank D also showed increased Flavobacteriaceae.

Sampled collected from the control tanks remained similar to the initial samples. In both control tanks, the dominant family remained unchanged (Alteromonadaceae for tank B, Pelagibacteraceae for tank C). The relative stability of communities in the control tanks increases our confidence in concluding that the changes in treated tanks were caused by the addition of live sand and mud.

One of the most interesting findings is a recent addition. In revisiting the new data for tank C I realized I had previously overlooked an important benefit of this treatment. Live sand & mud increased the amount of nitrite-oxidizing bacteria (NOB) in the treated tanks. See the following figure, which simply extracts the NOB data from standard AquaBiomics tests before and after the change in each tank.

It's a pretty dramatic change: tanks A and D had no detectable NOB before the addition of live sand & mud, but had normal to high levels after adding this material. The untreated tanks showed no such increase during the same time -- in fact, one of them (B) was initially present at low levels and undetectable in the later sample.

Tank D also showed a large increase in ammonia-oxidizing microbes (AOA & AOB). This change (not shown) was less impressive visually because all samples had detectable levels of AOA & AOB before the addition of live sand & mud.

Conclusions
It probably wouldnt surprise anyone that adding live sand and mud to the aquarium affects the community. I doubt anyone could have predicted exactly which changes would occur from adding this material. I sure couldn't have.

I've summarized the effects of these treatments in the following table, to let the reader draw their own conclusions.

	Untreated		Live sand & mud
	Tank B	Tank C	Tank A	Tank D
Change in dominant family	no	no	yes	yes
Alteromonadaceae	increased	increased	decreased	decreased
Pelagibacteraceae	decreased	decreased	increased	increased
Nitrite-oxidizing bacteria	decreased	unchanged	increased	increased

I conclude that the treatments accomplished got exactly the kind of changes I was hoping for -- I got lucky.



Did they improve the health of the tanks? That's another question and a more difficult one. The tanks are so different it would be hard to compare them in terms of benefits. I will say that both tanks have showed marked reductions in problem algae. Tank A had cyano on the sandbed, and the frag tray in Tank B had a variety of problem algae. Subjectively, without any measurements, both have improved. But I lack controls for that effect (i.e. untreated tanks with algal problems) so we can't attribute those benefits to the treatment. Certainly no harm done, and subjectively both tanks are doing well and arguably better than before.

I make no strong claims about any benefits on the general health of the tanks. Its too soon to say. But I was happy with the effects on the microbial communities themselves, and thought I'd share.