Macro growth stopping

[etmanning1]

A little over a month ago, I added a 40 gallon fuge to my 90g reef. It is lit by a 10,000K 250W metal halide.

I put two baseball sized chaeto portions to start the growth and then later added two types of caulerpa.

The chaeto initially exploded in growth and more than quadrupled in size. Both species of caulerpa have been steadily growing since I introduced them, but fairly slowly.

About 3-4 weeks after the initial growth explosion, the algae has more or less completely stopped growing. There is still a considerable algal growth on my glass in my DT so I’m assuming that there are still available nutrients in my system.

Could iron be a limiting factor for my macro growth?

Should I begin iron dosing and if so, what should I dose? I read Randy’s article on this and am more confused than anything.

 

[CiCikl85]

In my opinion I would never add any additives unless I can test for that particular element but the problem is some of those kits are expensive, how much are you feeding an are you running GFO? Was the macroalgae added to resolve a preexisting algae/nutrient issue?

 

[Fourstars]

I dos iron, if the DT still has algae then it is out completing you refugium. I would increase light for the fuge and may decrease the halide run time until things get under control. Also make sure you have enough flow through the sump. Light is more likely the limiting factor.

 

[Chuk]

I would try trimming the chaeto back. If my chaeto mound gets too large it seems to stop growing. Every 3 weeks or so I trim is by 75-80%. I've never kept caulerpa so I'm not sure about that stuff.

 

[Randy Holmes-Farley Verified Community Expert]

Iron dosing is a fine experiment. As to testing, that's not needed for iron, and probably not even useful. I dosed it and would only be able to detect it by ICP right after dosing. When I actually tested, none was observed, since no method we use can detect NSW levels.

A different trace element might also be limiting, or even low N or P (are you measuring nitrate and/or phosphate?)

I also found that my caulepra outcompeted by chaeto, and the chaeto died out while the caulerpa thrived.

 

[etmanning1]

Am not running GFO anymore, I used to (6 months ago) but have since stopped.

The refugium was added on more as an upgrade to my system than in order to combat algae growth. In general my DT has little algae, the glass just Gunks up every couple days quite quickly.

I do not test for PO4 or NO3. Never have felt the need to. That being said, my system is likely pretty nutrient heavy.

I feed fairly lightly, only about a 1/2” X 1/2” section of LRS a day ( probably equivalent to 3/4 of a frozen cube)

@Fourstars I don’t think I can increase the fuge lighting much more, I see people growing macro under cfl bulbs so I’m pretty sure a 250W halide is more than enough for the algae.

@Chuk the chaeto is nowhere near filling my fuge. It’s probably only about 1/4 if that of the total area. I did cut a section off the other day to give away though, I’ll see if that makes a difference in growth.

@Randy you’re saying I should be fine to just give it on dosing a shot and see what it does? In your article I did read that you seem to have found no negative effects. What would you recommend using to dose?

 

[Fourstars]

Sorry I thought the halide was on the tank. your right, that should do it. If you feed lightly then your growth should be less. Do you tumble? Increased flow helped my growth.

 

[Randy Holmes-Farley Verified Community Expert]

You may have become growth limiting in N or P for the macroalgae.

@Randy you’re saying I should be fine to just give it on dosing a shot and see what it does? In your article I did read that you seem to have found no negative effects. What would you recommend using to dose?

Yes. Here's my DIY recipe:

I personally would not dose enough to detect with a kit. The range is too high (IMO).

Trial and error is one reasonable way to see if iron is useful (actually, I don't know of any other, really).

Here's a DIY recipe:
Buy Fergon iron tablets from the drug store.
Put one pill in about 25 mL fresh water (volume is not that important since dose is not that important for iron). Let it soak for a while or overnight until the tablet breaks apart.

Swirl it to mix. Let is settle overnight. Then use the clear greenish liquid.

Dose about 1 mL per 100 gallons once a week (dose is not critical).

 

[etmanning1]

Okay I’ll try that. Thank you. If I don’t see an increase in growth I will get P and N kits and see if that’s the limiting factor.

 

[etmanning1]

I also found that my caulepra outcompeted by chaeto, and the chaeto died out while the caulerpa thrived.

Sorry for all these questions. I just made the solution to dose and with your instructions, one capsule would last 10-15 weeks? Can this stuff even store for that long or is it better to just mix up a new solution every week or two and discard the old batch?

 

[Randy Holmes-Farley Verified Community Expert]

Sorry for all these questions. I just made the solution to dose and with your instructions, one capsule would last 10-15 weeks? Can this stuff even store for that long or is it better to just mix up a new solution every week or two and discard the old batch?

In a closed container it will last a while (mine did), but if it gets brown and gunky (from air oxidation of the iron to ferric iron that precipitates as iron oxide), I'd start a new tablet.