Interesting changes (seemingly after lighting upgrade)

[cd77]

I recently upgraded from a 48" Coralife PC fixture to a 7 bulb Aquactinics T5 fixture. A few days after the upgrade, I'm starting to see some interesting changes -- I have no idea whether or not they are related, but am curious to hear peoples thoughts:

1. Of most interest, I'm seeing tons of small bubbles rising from the sand bed (~6" DSB) The tank is only 3 months old, is it possible I'm seeing denitrification from the SB so quickly -- my hunch is that this isn't nitrogen. Normal part of the maturing process, or? Would extra lighting, or the fact that diatoms seem to be going away cause any type of gas release?
2. My diatoms are retreating -- fast! Did the extra lighting speed cause the diatoms to metabolize any remaining silicates faster? (or does that even make sense?)
3. Likely unrelated, but worth mentioning just cause I like finding new stuff in the tank -- I saw my first bristle worm today.

[riley290]

bubbles in the sand can mean many different organisms but are a product of cellular respiration. most likely you're seeing some cyano or other sand microalgaes as their waste is bubbling to the surface. This could definitely be attributed to the lighting change.

[cd77]

Do you think I may have sparked the beginning of a big microalgae bloom?

[SaltyDr]

Lighting changes often spark a "minicycle" of sorts. Just keep on with normal maintenance and all should be fine.

[cd77]

Hmm.. I haven't done ammonia or nitrite tests recently. I think I'll make that a priority for tomorrow.

[stevensun]

The bubbles are very likely to be the mechanism of microalgea propagation. This kind of microalgea usually forms a film on the water surface and the bubbles are what they produce and use to bring them to the surface. The surface film can reduce the gas exchange taking place on the surface and keep the water temperature high. The lighting change is very likely to trigger the bloom though.

[danch]

The bubbles are most likely oxygen - normal byproduct of photosynthesis. More light means more photosynthesis, thus more oxygen produced.

The diatom recession is probably not directly related to the lighting change, but more to the point your tank is at in terms of maturation. You may see some other algae types bloom.

[riley290]

just to add. The lighting change probably has more to do with the quantity of algae and algal byproducts than the type, although different lighting may alter certain populations. Even had you kept your old lighting your tank will continue to go through algal blooms, most likely in successive orders, until a stable equilibrium is reached. Things that can disrupt this are stocking changes, light and feeding changes, flow changes, pretty much everything.

[cd77]

<a href=showthread.php?s=&postid=11101426#post11101426 target=_blank>Originally posted</a> by stevensun
The bubbles are very likely to be the mechanism of microalgea propagation. This kind of microalgea usually forms a film on the water surface and the bubbles are what they produce and use to bring them to the surface. The surface film can reduce the gas exchange taking place on the surface and keep the water temperature high. The lighting change is very likely to trigger the bloom though.
This seems to be exactly what is happening. A few days ago I ran a rake across the bubbles just to see the reaction and I noticed the sand is also clumping. Raking it causes the bubbles to release from the sand to the surface and even brings up small clumps of sand. A friend suggested red slime algae, though it's not slimy and only the sand (no LR, glass, etc..) are effected.

Should I keep raking the sand until this problem disappears? I don't want it to destroy my DSB. Should I just let it go?

Another thought I had was perhaps a precipitation incident causing the sand to solidify? pH is now getting higher during the day (almost to 8.3) AWT showed my calcium at 493 and Ca at 3.12meq/L. I've since stopped all kalk.

[danch]

pH is climbing during the day because the algae are consuming CO2, which is present partly as carbonic acid. Just like in a planted tank, where you inject CO2 to aid plant growth. And, just like in a planted tank with high light and lots of available carbon, the photosynthetic 'plants' are 'pearling'.

One of the things that can make your sandbed clump is simply the variety of bacteria and algae living in it. Some of these microbes have a sticky coating that causes sand grains to stick together. No big deal - you'll get pods that will forage through there are redistribute the sand grains. Don't bother raking your sandbed.

Do you have anything in the tank that would use a lot of calcium? If not, I'd expect Ca to climb if you're dosing kalk.

[cd77]

Thank you for the reply :)

I've since stopped dosing kalk -- a couple weeks now, so hopefully Ca will be going down. I still need to test my makeup water (1.0264 Reef Crystals) to ensure that the Ca isn't spiked with a bad batch of SW.

I'll leave the sand bed as it is, though I fear the entire layer will solidify (as it did before I [foolishly I suppose] raked it) and I just hope it doesn't completely kill-off all of the good aerobic bacteria living in it.

My Salifert Ca kit comes in today so I should be able to get a good idea where Ca is really at. AWT showed my Ca at over 490, while the same API test showed it much lower than that.

[trd47]

i went through the same experience. my tank is now 3 months old!

anyway i was doing what you were doing raking to get rid of the bubbles and to stir up the sand because my white sand was turning brown (diatoms)! then one day i decided to see what happens if i don't disturb the sand (per friends and ppl on reefcentral), sand got browner and one day my say was getting white and whiter! if i remember correctly it took about 2 weeks for this process to finish if you will. i do not know however if your process will take 2 weeks because i had a sand bed about 2inches deep, it may or may not play a factor.

take home message its all normal and it'll disappear.

[cd77]

trd47 -- was your sand clumping as well?