acropora tenuis getting thin and white - need advice

[amir basis]

hey everyone,

so here is the thing, 3 weeks ago i bought my first ever acropora tenuis (with a few more sps corals). in the last few days the coral started to look "thin", the tissue in the top branches became more and more translucent and it was possible to start seeing the skeleton's structure. today some of those branches started to bleach. the whole process is relatively slow in comparison to RTN.

now what is more mysterious to me is that the polyps extension on most of the coral is good, and the coral responds well to direct feeding with frozen and finely grinded foods, with mucus secretion and prey capture is also visible.other corals seem to be doing just fine

the aquarium is located in an outside greenhouse, and right now i'm using a simple 460 nm LED strip to give a little extra light since the solar intensity right now is weak during the winter days.
i did a 45% water change today and here are the parameters and general information about the system :

-age: 1 year
-volume : 250 liters
-light: sunlight, LED as extra during winter
-fish : 1 juvenile emperor angelfish, 1 yellow tang, 2 clownfish, 1 peprmint shrimp
-coralline algae : growing like crazy for the past 6 months
-temp': 23-24 c
salinity : 35.5 ppt (red sea salt)
-Alk: 7.4 DKH
-Cal: 420 ppm
-Mag: 1540
-Po4: 0.05-0.08
-No3 : 0.5-0.8
-water source : RODI

i kinda suspect that it might be a combination of too much light and low nutrients...what do you all think? i'm worried i might loos it

here are some pictures of the coral and the system, i've tried my best to take good ones but its hard without a filter. the pic are taken under sunlight and blue LED:

many thanks

 

[East1]

it looks like quite a clean system, and your nitrates are very low - I'd suggest increasing nitrate slightly in the morning (the tank will consume them fairly fast) but to coincide with the highest period of light, in addition I'd recommend checking your iodine and potassium levels too as these can cause metabolic upset in acropora.

Tenius are a very heavy-feeding coral, they require nutrient in the water - no3 and some po4, as well as foods they can capture. The bleaching from the tips like this is likely a higher rate of growth of the skeleton than tissue, you'll sometimes see this from a cause when alk is too high and no3 is too low, especially if it spikes youll see 'powdery tips', but chances are getting high light via sunlight with low NO3 is causing excess skeletal aggregation that exceeds the growth rate of the tissue

It's useful to remember that kH in the form of bicarbonates is what is broken down for co2, especially in the growing tips which is why you see tabling corals with a far lighter rim of growth. When there's an imbalance like this outside of natural limits it can cause something like this at the growing tip, but if it's not from the base it's less of a worry because basal recession is usually starvation from low po4, or potassium/iodine

 

[amir basis]

thank you so much for your answer,

i did forget to mention that i use a chaeto refugium as an export method, and i got to say that i don't monitor iron nor iodine.
i kinda doubt it that its fast growth that is outcompeting the tissue, cause here and there it also visible in the middle of the branch, but then again i have now experience with tenuis.
would you suggest using kno3 or any other method for raising the no3 levels?

 

[amir basis]

any recommended potassium, iodine and iron test kit btw?

 

[Pkunk35]

Are those mariculture colonies? If so many many people have this issue when bringing them into home aquaria.

 

[amir basis]

so i have red lately, i'm not quit sure if they are mariculture but they are originated from Australia (acording to my lfs), means anything?

 

[Charlie’s Frags]

I suggest you get a bunch more fish
Tenuis love fish poop

 

[amir basis]

I suggest you get a bunch more fish
Tenuis love fish poop

i suppose i can't just pee myself in the tank LOL,
will do, thought maybe adding a blue tang and a few blue chromis

 

[lemonade]

I like the idea of this tank, but just from the looks of it you’re going to have a tough time keeping acropora imo. No sand, and no real reef rock makes for a very sterile system. Adding more fish and/or feeding more may help, but having sand or some old LR would really help you out. It looks like you’re going for a minimalistic look but the old 1lb of LR per gallon really is effective. I’d find a way to add sand or more rock even if you have to put it in the sump.

 

[Pkunk35]

so i have red lately, i'm not quit sure if they are mariculture but they are originated from Australia (acording to my lfs), means anything?

So I don't know much about origination or where mariculture is being grown, I imagine Australia to be one such place .

Did they come on a rock base or have a metal tag?

Edit: IMO when I read the specs on the tank, I don't think I would add any big fish to resolve this issue only because the tank is fairly small. The juve emporer will get very big. I say keep feeding your existing fish and keep things consistent water quality wise for the coral. If you have a good looking chunk off of a dying colony then frag it.

 

[amir basis]

So I don't know much about origination or where mariculture is being grown, I imagine Australia to be one such place .

Did they come on a rock base or have a metal tag?

no they did not, they simply came as a big fragged branch not glued to anything.

 

[amir basis]

I like the idea of this tank, but just from the looks of it you’re going to have a tough time keeping acropora imo. No sand, and no real reef rock makes for a very sterile system. Adding more fish and/or feeding more may help, but having sand or some old LR would really help you out. It looks like you’re going for a minimalistic look but the old 1lb of LR per gallon really is effective. I’d find a way to add sand or more rock even if you have to put it in the sump.

hmm, so you'r saying that more rock would be beneficial for more bacteria/ stable parameters?

the reason i didn't add any sand in the first place was because after a while they become a huge battery of waste and decaying matter, and the hassle of syphoning and cleaning it every time just isn't worth it IMHO. however i do have plenty of extra space in the sump for additional rocks.

 

[lemonade]

hmm, so you'r saying that more rock would be beneficial for more bacteria/ stable parameters?

the reason i didn't add any sand in the first place was because after a while they become a huge battery of waste and decaying matter, and the hassle of syphoning and cleaning it every time just isn't worth it IMHO. however i do have plenty of extra space in the sump for additional rocks.

Yes, exactly. Mature LR holds so much beneficial bacteria, and places for micro life to thrive. This keeps a constant supply of available foods for your coral, and really helps from ever having to worry about hitting rock bottom with nutrients. As for a sand bed it really depends, if too much food makes its way into the sand instead of being eaten it can get nasty. However, I really think it does help keep everything in balance and benefits the whole mini ecosystem we try to create when you have a healthy sand bed.

 

[amir basis]

Edit: IMO when I read the specs on the tank, I don't think I would add any big fish to resolve this issue only because the tank is fairly small. The juve emporer will get very big. I say keep feeding your existing fish and keep things consistent water quality wise for the coral. If you have a good looking chunk off of a dying colony then frag it.

i've just noticed your note,
ya i didn't plan going on and getting a big fish cause i don't wanna overshoot and get the water with too hight no3/po4 levels, and of course because the tank is small. the emperor angelfish is there on limited time cause i plan on finding a new bigger home for it once it gets a little bigger.

i'm only wondering if i should in the meanwhile use any KNo3/NaNo3 to ramp up a little my no3 levels (lets say to 2 ppm), if that's indeed my problem, and to reduce the lighting hours on my refuge, or it might do more harm than good?

 

[East1]

if that's indeed my problem, and to reduce the lighting hours on my refuge, or it might do more harm than good?

if you dose NO3, you don't also reduce the light, you want to find balance between the light you have it at, and the amount of NO3 required to create balance in the system for the corals

If you also have cheato and you don't test then I'd really recommend testing iron, and also iodine and dosing those. For this specific tank, I'd recommend KZ Potassium Iodide Flouride - it's inorganic so it won't fuel algae and diatoms but the corals will benefit, and the effect can be increased mixing it with Coral Booster by KZ to make it more available to the corals, use the same dosage as you would normally.

This pale colour in your other coral and this look are from low nutrients (nitrate, and the above) and because the system is sterile. You can compensate for a sterile system by adding KNO3 and also a phosphate source and then limiting it by dosing carbon, to create a cycling of nutrient through the system, it's the cyling of nutrient that is important to corals, for example dosing iodine that is later assimilated into cheato, t here is always a trace amount that the coral can use, if it is not getting it from food it can catch.

For this I use Easylife Nitro and Phospho, be careful because for saltwater they are very concentrated. I use 1/10th of a drop for 5 gallons of phospho and 1 drop of nitro, daily with a good carbon source) and then limiting it by dosing carbon.

Adding fish won't help because the issue is bioavailable macronutrients and micronutrients and the cycle from fish eating to bioavailable forms of what the coral require take a few weeks which will stress this coral. These corals are showing this because they come from mariculture where they have access to a lot of food, within this tank there is limited microfauna, and the bacterial populataion and algal population on the glass etc looks young.

Essentially, your tank can support and grow acropora, but the biology is unstable and because there is no other source of important element cycling through the system (nitrogen, phosphor, iron, iodine, potentially potassium) the corals are reducing it from the water.

This reduction is sped from high lighting causing high motablism, they are not able to store enough nutrient and so they are essentially starting to consume themselves. this is why the tissue is not growing fast enough to protect the tips, I'm not sure the exact mechanism for this but I have some theories to do pH and CO2 in the cells, because similar happens if you spike alklinity and nitrate is low, when there is nitrate present it seems to fuel the internal algaes which support the coral and provide a buffer of some sort.

 

[amir basis]

if you dose NO3, you don't also reduce the light, you want to find balance between the light you have it at, and the amount of NO3 required to create balance in the system for the corals

If you also have cheato and you don't test then I'd really recommend testing iron, and also iodine and dosing those. For this specific tank, I'd recommend KZ Potassium Iodide Flouride - it's inorganic so it won't fuel algae and diatoms but the corals will benefit, and the effect can be increased mixing it with Coral Booster by KZ to make it more available to the corals, use the same dosage as you would normally.

This pale colour in your other coral and this look are from low nutrients (nitrate, and the above) and because the system is sterile. You can compensate for a sterile system by adding KNO3 and also a phosphate source and then limiting it by dosing carbon, to create a cycling of nutrient through the system, it's the cyling of nutrient that is important to corals, for example dosing iodine that is later assimilated into cheato, t here is always a trace amount that the coral can use, if it is not getting it from food it can catch.

For this I use Easylife Nitro and Phospho, be careful because for saltwater they are very concentrated. I use 1/10th of a drop for 5 gallons of phospho and 1 drop of nitro, daily with a good carbon source) and then limiting it by dosing carbon.

Adding fish won't help because the issue is bioavailable macronutrients and micronutrients and the cycle from fish eating to bioavailable forms of what the coral require take a few weeks which will stress this coral. These corals are showing this because they come from mariculture where they have access to a lot of food, within this tank there is limited microfauna, and the bacterial populataion and algal population on the glass etc looks young.

Essentially, your tank can support and grow acropora, but the biology is unstable and because there is no other source of important element cycling through the system (nitrogen, phosphor, iron, iodine, potentially potassium) the corals are reducing it from the water.

This reduction is sped from high lighting causing high motablism, they are not able to store enough nutrient and so they are essentially starting to consume themselves. this is why the tissue is not growing fast enough to protect the tips, I'm not sure the exact mechanism for this but I have some theories to do pH and CO2 in the cells, because similar happens if you spike alklinity and nitrate is low, when there is nitrate present it seems to fuel the internal algaes which support the coral and provide a buffer of some sort.

Many thanks for your answer

I’ve ordered the Red Sea trace elements test kit for iron, potassium and iodine.I was pretty blind to the fact the chaeto might deplete trace elements from the water by itself.

I’ll look for a good source for kno3. I could have just picked one from my gardening supply shop But i don’t trust the grade of the materials there to use it in the tank.

that’s very interesting what you are saying about higher metabolism when the coral is subjected to higher light/Alk with low availability of nutrients . It kinda sound like pushing full throttle with the engine air suction clogged up.not good.
Basically what your saying is , if I understood you right, it might be better if I push the tank towards a more “heavy in heavy out” routine.
I do however wanna mention that the rocks are full with copipods and other microfuna , yet I do think the these rocks aren’t the best type. For some reason while I do have plenty of coralline algae growing on my wavemaker and lumps (especially the inside of the skimmer down the sump), it’s almost none visible on the rocks themselves

 

[East1]

Iron is quite reactive, so you might see 0, but just dose enough that you pick up a small amount a n hour after dosing, iodine I usually never pick up in test kits because it gets assimilated into bacteria and microalgae fast, I just dose KZ PIF every second day and it seems to keep balance

 

[amir basis]

I’ll give KZ PIF a shot and I’ll add kno3 to increase the nitrate level to around 4 ppm slowly over a course of a week .
we’ll see how it goes.

 

[East1]

Sounds good, one thing to note if you look at your coral very carefully when you dose, when you find the element that the coral is missing it’ll almost look like it’s flesh is thicker and more robust within a few minutes of dosing, that’s how you’ll know which of the elements above is most limited

nitrate will get consumed very fast so it’s something to maintain a regular dose too

 

[lemonade]

I’ll give KZ PIF a shot and I’ll add kno3 to increase the nitrate level to around 4 ppm slowly over a course of a week .
we’ll see how it goes.

I’d be careful going this route with mariculture pieces. Chasing numbers is not what you want to do with Acropora, especially ocean grown. Keep it simple. Your numbers all look good you just need a more established and plentiful bio load. One year is not much for a reef tanks maturity to set in. Feed your fish multiple times a day until they are full, and find a way to get some more LR either from an older system or from the ocean. As long as you’re keeping KH in the mid 7s and have that natural sunlight the corals have a good chance at holding on even with low No3. Just keep up with the feeding