I've been having cyno issues for quit some time in my fuge. Not a real biggy until now as I'm trying to maintain a decent pod population and my cheato won't grow.
I messed it up a long time ago by adding a heavy dose of salt trying to raise my salinity. Stupid move I know. Wound up killing everything off. Anyways....it hasn't been right since.
Today I took my intake pump off to clean it, fuge had no flow for a couple of hours at the most. Scraped some cyno off the fuge walls too. Well just now 2:30am I take a look see and all the cyno is dead, along with a bunch of amphipods and very inactive bristle worms. WTH?
Question is...do I tear it down, completely clean it out and add new sand and LR/cheato. Something just isn't right with it. I'm afraid it's going to start affecting my DT.
I do have a lil canister filter hooked up an running some carbon in the DT/ChemiPure elite, just in case.
I've not touched it in any way as far as cleaning it out. But I really need to do it. It's just that's its so small that it would empty out in a minute via siphoning
A quick note on siphoning of small areas like this... a turkey baster is your friend, they can siphon a small area.
So... is it just the bulb that's two months old, or is it the entire HOB fuge that's only two months old? If the whole fuge is only two months old, I would propose to just leave it be, siphon out as much of the cyano as possible, and try to give it another month or two. If the fuge is older, and just the bulb is newer, then the below could be considered as you wish.
First would be to remove the 2" of pink aragonite substrate and either leave that area empty and have just the chaeto in there, or replace it with only 1/2" of substrate, or at least a 4" deep bed with some extra critters. Cyano thrive in two types of environments in particular:
Environments with a great deal of freely available PO4 / Phosphates, and
anoxic environments in where freel available nitrogen is very depleted
With the 2" substrate bed you have in there, it is very possible that the entire bed in the fuge has become an anoxic zone, especially with the low flow through the fuge. With a shallower bed of 1/2", it will not be anoxic, rather, it will always be aerobic and less conducive to the growth of cyanobacteria. Conversely, with a 4+" substrate bed in the fuge, the bottom several inches of the bed will become anoxic but there will be a better opportunity for the top 1/2" or so to maintain some aerobic activity, helping reduce a cyano-conducive environment. With the deeper bed, it would also be a good idea to add 2~4 nassarius snails or other sort of natural substrate sifter.
Other things to consider in general include:
PO4 levels... these can be brought down by feeding less or changing what you are feeding or skimming more heavily, slightly wetter than normal.
If that 18W CF bulb is a standard 10,000K bulb or similar, that's probably fine but if it is a generic cool white or warm white bulb from Home Depot, etc. the spectrum of the light probably isn't helping any.
The inlet compartment and outlet compartment of the fuge... detritus can build up in those areas. As detritus breaks down, it can become a source of PO4. It is a good idea to siphon those areas out every water change.
Hope some of this helps... at least maybe it can spark some thought for consideration.
The fuge itself is over a year old. The lamp is a Coralife 10k. Would removing the top 1/2" or 1" of the substrate in the fuge cause any issues? Don't want to be releasing anything nasty from underneath.
Part of me feels I should tear it up and start over with it. At least get rid of the substrate and add some new and less of it. My DT is pretty well established.
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