Shrinking Nems, I think lighting is the issue, please HELP!


New member
I have three nems in my reef tank, 1 RBAT and 2 x Haddoni, and they have all been doing well, still have good color, not bleached, and all still eat. The issue is that they have all been slowly shrinking.

The RBTA had shrunk and started bleaching, so I upgraded my lights to the HIPARGERO (did have 18W PAR38 bulbs x2). Since then the RBTA has started to color back up, but now the Haddoni's have shrunk. The oldest one was about 7" across when open, now it only opens to about 4". It has been in the tank for ~10 months. The other was about 12" across and has only shrunk a little bit to about 10". It has been in the tank about 4 months.

I have tried scouring the forums for answers and I think that I have come to the conclusion that the issue is with my lights.

Here are my system params:

40B - running ~15 months
20L sump
Curve 5 Elite Skimmer
~40lbs live rock
~40lbs live sand
Vortech MP40WQD
Jebao OW-25 wavemaker

Live Stock:
Pair of Spotcinclus clowns
Melanurus Wrasse
Several snails and crabs
Brittle starfish
Aussie Gold tip torch
Several Acan Colonies
Indo Fuzzy Mushrooms

If I remember correctly from my last testing (I will retest tonight and update id different)
Temp - 78
SG - 1.026
Ammonia - 0
Nitrites - 0
Nitrates - <5
Calc - 500
Mag - 1450
Alk - 8

I do 25-50% water changes every 1-2 weeks using Red Sea Blue Bucket salt. I am thinking I may just go back to the lighting that has worked for me in the past, MH/T5. I am looking at a fixture with 1x 250W MH bulb and 4x 24W T5's. I was thinking I would use an Ushio 20K MH, and Geissman T5's, 1 x Aquablue Coral, 1 x Super Purple, and 2 x Super actinic. Do you all think this combo would work and look good. Please help me figure this out.

Other bulb recommendations or thoughts on other things that may be causing my nems trouble would also be appreciated.
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Moved on
Anemone shrinking is not necessary bad. A lot of it depends on condition of the tank.
The only thing you can do is to do adequate water change to ensure good stable chemistry. Feeding anemone, if they are healthy, will get them growing.


Crab Free Zone
Premium Member
Bleaching is the expelling of some/all the zoo.
Usually associated with too much light.
You can't give a nem too much light cause he will just move.

Now a change in lighting...yup.... that's not going to be a good thing in the short term.

WhAt they hate is any change in water chemistry, this they cannot move away from.

Your parameters look good, how stable are they and how long have they been that way.

What is your level of phosphate?
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New member
So you are both basically saying to leave the lighting the way it is and up my water change game, ensuring my params are as stable as possible?


New member
Also, just to clarify, I am not concerned that they are getting too much light. I am concerned that the lights I have are not sufficient for the nems.


Moved on
Not enough light for them will cause them to move. BTA does not require anywhere near the amount of light Haddoni like. Consider add spot light on the Haddoni.


Crab Free Zone
Premium Member
So you are both basically saying to leave the lighting the way it is and up my water change game, ensuring my params are as stable as possible?

Not as much the changing of water, but the stability.
Stability is everthing, Nems not much for change.

I noted that after stabilizing all 8 parameters, nothing ever contracts now and growth is very fast.


New member
I have 2 green BTAs under Chinese LED lights that are strong enough to bleach coralline, green, and red algae.
One of those decided to sit at the edge of the intense light zone where the flow is also rather mellow. The other settled smack in the center but so that it can retreat into the shade if needed. And the flow there is rather intense. The latter has gotten quite big over a short period of time while the other stayed pretty much the same. The one in the center is out for about half the day and then retreats into its cave.
The same lights with the same intensity settings are over the neighboring tank where I have 2 giganteas in recovery and they seem to be fine with it as well.
So I would say that BTA can handle a lot of light as long as they can get shade when they need it.
Haddoni are similar to giganteas in their light requirements but IME they don't like too much flow.

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