Mass die-off in nano reef tank - Help needed

[cptsteiny]

This will probably be a long post (and my first), hopefully I’m providing all the info you’ll need.

The basic issue is my coral and snails are dying rapidly, and the reason doesn’t seem to be obvious.

I set up my tank in November 2022 and have had two significant outbreaks of green algae. October 2023 was the beginning of the most recent outbreak and is basically still going. In November 2023 I noticed cyanobacteria taking over. I dosed Chemi-Clean and within a week the cyano was gone. However this is when the significant problems seemed to start. By December, all of my snails had died and I lost a Hammer coral and a Torch coral. My Zoanthids and Toadstools closed up almost entirely and haven’t opened since. I initially chalked this up to shock from the cyano.

In January, I added more snails and they all died within a couple of days. The Zoanthids are starting to die and flake off and one of my Toadstools is looking quite sick and is shriveled up.

I have a Fluval Evo 13.5, currently stocked with 2 clownfish, 4 gobies (2 types), 2 Toadstool corals (each a different variety), and Zoanthid corals. Filtration is: filter floss, Purigen bag, Chemi-Pure Blue bag.

I do a daily 2% water change with a 10% weekly change with substrate sifting (started doing the weekly change when the algae got really bad, used to be monthly). I use exclusively RODI water from a LFS.

I dose Brightwell MicroBacter Clean daily (since algae outbreak, used to be weekly), and Brightwell MicroBacter 7 weekly. I used to dose Reef Enhance and Live Rock Enhance, but stopped when everything started dying.

Tank parameters are tested weekly and are:
Salinity: 1.026
Ph: 8.3 (drifts between 8.1-8.3)
Alkalinity: 7.8 (fluctuates pretty bad, 7.5-8.5)
Ammonia: 0.003 ppm
Nitrites: 0.03 ppm
Nitrates: 5.3 ppm (fluctuated from 2-30, but hasn’t gone above 10 since December)
Phosphate: 0.2 ppm (fluctuates from 0.05-0.2 at a high point at the moment)
Calcium: 550 ppm (fairly stable)
Magnesium: 1350 ppm (fairly stable)

I recently had my water ICP tested by Triton and here are the outliers:
Tin: 9 micrograms/l (high)
Iodine: 23 micrograms/l (low)
Barium: 62 micrograms/l (high)
Silicon: 2500 micrograms/l (very high)

The fish are doing fine, no observed issues. I feed them DKI pellets and they are minimally fed at the moment as I try to combat this algae ( they eat all the good within 2 minutes).

Any ideas on what is going on?

 

[Mr. Mojo Rising]

Fish are more hardy than corals and inverts, so fish being fine while corals and inverts die indicates a water quality issue to me.

big alk shift as you mention, corals hate that. Nitrate is very low, and phosphate very high, which explains the algae. The tank is very overstocked with 6 fish, its good you are doing daily and weekly water changes, the evo filtration system is not adequate enough to handle the bioload.

Pellets has more phosphate, and fuels algae more, try frozen foods. I would not suggest to cut the feeding down, but instead feed less amount of food but feed more often.

Honestly I would suggest to get your own rodi machine and mix your own salt. Who knows how often the LFS changes their filters, or if they switch salts every time, you have no control over the water quality. RO buddy is an inexpensive apartment size unit that connects to the tap on the sink.

I'm also curious about your flow, do you have a powerhead in the tank? How do you oxygenate the water? Heavy algae lowers oxygen levels at night.

A tank pic will really help get more ideas. I don't think its one single thing that is the issue here, I think its a few things going on ......

 

[Lavey29]

I agree with the above and you don't need purigen if you are using chemipure blue it already contains purigen. You are stripping elements from your water.

 

[cptsteiny]

Thanks for the replies.

Almost nothing on this Evo is stock since I knew at the beginning its filtration and pump were fairly worthless. The filtration I’m using in order of flow is: dual density filter floss (overflow falls onto it and I rinse almost daily and replace monthly), Purigen bag, Chemi-Pure Blue bag, Seachem matrix rocks, return pump. I’ve changed filtration a little over time. I used to do just the Purigen and an activated carbon bag (no Chemi-Pure). Could get rid of the Purigen, but figured I’d keep it given where my phosphates are. I have tried a small refugium, but couldn’t keep the chaeto contained or alive, but willing to try again.

I welcome filtration suggestions.

Flow has always been a question for me. My return pump is a Syncra Silent 1.0 (250 gph) with a Y adjustable return nozzle with flat heads that are aimed between my coral and toward the front (see image). I have a Jebao SW-2 wavemaker pushing probably 150-200 gph (adjustable between 130-800), this is in the back of the tank pushing water behind the rocks. I don’t really notice any debris accumulating, even under the bridge rock. But I never know what flow is enough or too little. I haven’t changed it much and not since before everything seemed to start going bad.

The gobies are all nano, so I’m surprised the bio load might be high.

I mix my own saltwater (Two Little Fishes) and get the RODI from the LFS. The LFS is more of a distributor with huge tanks, I really can’t imagine they’re using a bad RODI system since their business depends on it, but I guess it’s a possibility.

 

[Mr. Mojo Rising]

The first thing is to help oxygenate the water, your fish are at the surface gasping for air. You need a powerhead in there, pointed up at the surface to create surface agitation and oxygenate the water. The water should look like rapids.

Flat water in general is bad, it cuts air exchange, as well as decrease the light effectiveness (for corals).

Corals and inverts also need oxygen, and they need flow to bring the oxygen and nutrients to them. Put that powerhead in the display tank and break up the water surface, your tank in general will be healthier for it.

 

[cptsteiny]

I went ahead and pointed one of the return nozzles asking the surface.

Although not really sure that was the issue. The fish are almost never at the surface except during feeding (which is probably why they were in that image, I was near the tank). I feel like I should get pretty good oxygenation with the overflow since that’s pretty turbulent. But I am pretty new here. Anyway, surface looks pretty agitated now.

 

[Mikeltee]

Consider a gyre. One is all you need. I use the 90 in a 40gal and it keeps everything stirred up real well. It's placed at the top and points up. If that tank is 24" you can use the 70. Yiu would just turn it down. These are pretty sweet!