Struggling to Balance: Alk, Ca, Mg, ORP & PH

[johnacharles93]

Hello fellow reefers,

I’m reaching out for help dialing in the chemistry and filtration balance on my 65-gallon Waterbox AIO mixed reef tank. I’ve been working hard to stabilize parameters, reduce algae, maintain water clarity, and support healthy coral growth but I’m hitting some roadblocks and would love expert guidance.

Here’s a detailed snapshot of my current system:

​

System Overview​

Tank: 65g Waterbox AIO​

• Lighting: AI Prime HD16 Reef (3)
• Flow: Dual Nero 5s
• Filtration: 4 filter socks, Sicce Shark 300 skimmer, carbon bag, 2 foam sponges
• Dosing: Manual ESV B-Ionic 2-part + Magnesium (started this week at 150ml)
• Controller: Apex + Trident (not always aligned with manual tests)
• ATO: With RODI from my 7 stage filter
• Goal: Stable chemistry, low maintenance, automated where possible

Livestock:​

Fish:

• Biota Hippo Tang (1.5”)
• Scopas Tang (4”)
• Snowflake Storm Clownfish pair
• Mandarin Dragonet
• Midas Blenny
• Royal Gramma
• Bicolor Angelfish
• Pink Spot Goby
• Pink Anthias
• Inverts: Blood Shrimp, snails & crabs (CUC)
• Corals: Mix of LPS, softies, some SPS (GSP, Ricordea, Acro, Frogspawn, Duncan)

Recent Parameter Readings​

• Alkalinity: 8.6–9.46 dKH (Salifert and Trident readings vary slightly)
• Calcium: 450–522 ppm
• Magnesium: 1080–1200 ppm (Salifert consistently higher than Apex/Trident)
• pH: ~8.04
• Phosphate: 0.03 ppm
• Nitrate: 10–25 ppm (fluctuates by test duration and time of day)
• Salinity: Stable
• Temp: ~78-80 °F

Current Challenges​

Cloudy water occasionally after magnesium dosing

• Brown algae on sand despite low nutrients
• Some coral retraction (notably Frogspawn & Duncan)
• Inconsistent Mg readings (Salifert vs Apex)
• Desire for clearer water & stronger coral growth
• Manual dosing swings may be affecting stability
• Tired of filter socks looking for better filtration options
• Considering CO₂ scrubber to improve pH/oxygen levels

Questions & Advice Needed​

1. Test Accuracy – Can I trust my Salifert Mg over Apex if there’s a consistent 100+ ppm difference?
2. Precipitation Risk – Is cloudiness after Mg dosing a red flag for precipitation?
3. Filtration – What are solid alternatives to filter socks in an AIO tank that will help with detritus and water clarity?
4. CO₂ Scrubber – Worth adding to maintain higher pH/stability? Any product recommendations for AIO setups?
5. Dosing Strategy – Would you suggest switching to automated dosing or just adjusting my ESV routine and volumes? I already have Alk and Ca being dosed through the Apex.
6. Algae Control – How do I better balance nutrients and trace elements to prevent algae on the sand while still keeping corals fed and healthy?
7. Coral Growth – What chemistry improvements or nutrient tweaks might help enhance polyp extension and coloration?

Build Thread: My Build Thread


Thanks so much in advance! I’ve learned a lot from this community, and I’m hoping to get everything truly dialed in. I want a balanced, clean, thriving reef and I’m committed to doing the work. Open to feedback on anything I may have overlooked!

 

[Randy Holmes-Farley Verified Community Expert]

I'd be wary of assuming magnesium is that low (either one). Tests are often inaccurate. Try the magnesium kit on some new salt water.

Everything else is OK, though phosphate is borderline low.

 

[johnacharles93]

I'd be wary of assuming magnesium is that low (either one). Tests are often inaccurate. Try the magnesium kit on some new salt water.

Everything else is OK, though phosphate is borderline low.

I am using Instant Ocean - Reef Crystals at a ratio of 1/2 cup : 1 gal. It should be around 1200ppm but I will check before my next water change.

 

[thedon986]

Your low nutrients is likely the cause of the brown algae on the sand, which is likely dinoflagellates. Dinos love low phosphate. Invest in dosing pumps, raise phos and raise magnesium.

 

[Randy Holmes-Farley Verified Community Expert]

I am using Instant Ocean - Reef Crystals at a ratio of 1/2 cup : 1 gal. It should be around 1200ppm but I will check before my next water change.

Should be based on your kit? That is below what RC gives at 35 ppt.

https://www.reef2reef.com/threads/the-ultimate-salt-test.949805/

 

[timqmana]

Algae Control – How do I better balance nutrients and trace elements to prevent algae on the sand while still keeping corals fed and healthy?

You control algae with herbivores, not with nutrients and trace elements. You starve the algae, you starve the corals. Look into getting a conch for your sand bed and double check that it's actually algae and not dinos.