Brown Spots on Rocks and Zero Nitrates/Phosphates

[zoroi]

Hello,

I’ve had my aquarium for 46 days now, and I would really appreciate some help with some recent issues I’ve noticed.

My Aquarium:​

• Tank Dimensions: 80x40x40 cm + external sump (~40L)
• Lighting: 2x Spectra Knight V3
• Return Pump: Dymax 1800L/h
• Skimmer: 300 Ny do Brasil
• Circulation Pump: HSBAO 4000L/h with controller

Current Livestock:​

• Fish:
  • 1 Clownfish
  • 1 Firefish
  • New fish to be added to the main tank on Sunday
• Invertebrates:
  • 11 Hermit Crabs
  • 10 Snails
  • 1 Astraea Snail
• Corals:
  • 4 Zoanthids (added more recently)
  • 1 Trumpet Coral
  • 2 Torch Corals (added one more recently)
  • 1 Green Leather Coral
  • New Gonioporas added recently

Feeding and Dosing Routine:​

• Fish Food: Tropical brand, once daily (increased amount recently)
• Coral Food: Pellet coral food, twice a week
• Fuel Additive: Twice a week
• Fusion 1 and 2: Daily dosing
• Bacteria: Delta Fish and Stability dosed in the last few days

---

Recent Observations:​

1. Around 1–2 weeks ago, I noticed brown algae appearing in the tank. Over time, it started to disappear, and now there’s almost none left.
2. However, I’ve noticed small brown spots on the rocks starting to appear.

When I tested my parameters today, I found that nitrate and phosphate levels are at zero.

​

Current Parameters:​

• KH: 8.1
• Ca: 400
• Mg: 1175
• Ammonia: 0
• Nitrite: 0
• Nitrate: 0
• Phosphate: Close to zero or zero

​

My Actions So Far:​

1. Reduced the photo period of the lights to 10 hours.
2. Reduced the skimmer's efficiency slightly.
3. Increased feeding (I was feeding very little, only once per day).
4. Added a new fish to the quarantine tank, which will move to the main tank on Sunday.

​

My Questions:​

1. What could these brown spots on the rocks be? Could they still be brown algae?
2. Should I take any additional steps to address this issue?

Thanksss!!

 

[MD51]

Adding your fish will help balance things out. You may want to look into NeoNitrate & dosing Calcium & Mag to start

 

[TheDuude]

Diatoms are normal in a new reef tank.. I would aim to raise nitrate and phosphate so u dont end up with dinos

 

[zoroi]

Are these brown spots brown algae or could they be dinoflagellates?
Are my actions enough to raise nitrate and phosphate, or should I use a product to speed up the process? (I read that raising phosphate and nitrate too quickly might not be ideal)