Need help on fixing tank.

TheNewClownFish · 2026-10-06T11:56:12-0400

Hi everyone,

I’ve been in the hobby for a bit now. Surprisingly my tanks were usually fine but I took a year break, sold everything and got back into it. This time around, I’m having some slight issues that I’d love insight on how to approach.

I have a 18.5G Reef Tank. It’s running for two months. I use the Red Sea Coral Pro (purple bucket) and do 20% weekly water changes with my RODI. My TDS is 0. My tank is fully stocked (two medium/small clowns/firefish and a tiny tailspot blenny). They all get along well as they occupy different parts of the tank.

Issue: corals aren’t doing too well. Particularly, I’ve had hammers die twice. My GSP (I got a big colony) is doing fine and growing good

I also have some kind of algea (looks like diatoms but it’s not) that makes my sand bed terrible. It goes away after lights are off but comes back when it’s on. I did have bubbles on my rock that looked like Dino’s but that went away. I thought my nutrients were low but I have some film/turf algea growing at the back wall of my tank (not too bad though).

Surprisingly I’m seeing coraline take off in just two months.

I don’t have a nitrate or phosphate test kit. I also don’t have a UV sterilizer. Any tips on what to do, what to buy, etc? The pics are in reference to the sand bed issue (lights on vs off)

JTP424 · 2026-10-06T11:58:42-0400

What kind of light are you running?
Get a hanna checker for Nitrate and Phosphate (IMO)
Once you get those measurements we can be of help.

Mr. Mojo Rising · 2026-10-06T12:00:17-0400

Can you tell us about your lighting?
Are you testing alkalinity?

Baldyreef · 2026-10-06T12:01:53-0400

TheNewClownFish said:
Hi everyone,

I’ve been in the hobby for a bit now. Surprisingly my tanks were usually fine but I took a year break, sold everything and got back into it. This time around, I’m having some slight issues that I’d love insight on how to approach.

I have a 18.5G Reef Tank. It’s running for two months. I use the Red Sea Coral Pro (purple bucket) and do 20% weekly water changes with my RODI. My TDS is 0. My tank is fully stocked (two medium/small clowns/firefish and a tiny tailspot blenny). They all get along well as they occupy different parts of the tank.

Issue: corals aren’t doing too well. Particularly, I’ve had hammers die twice. My GSP (I got a big colony) is doing fine and growing good

I also have some kind of algea (looks like diatoms but it’s not) that makes my sand bed terrible. It goes away after lights are off but comes back when it’s on. I did have bubbles on my rock that looked like Dino’s but that went away. I thought my nutrients were low but I have some film/turf algea growing at the back wall of my tank (not too bad though).

Surprisingly I’m seeing coraline take off in just two months.

I don’t have a nitrate or phosphate test kit. I also don’t have a UV sterilizer. Any tips on what to do, what to buy, etc? The pics are in reference to the sand bed issue (lights on vs off)

the disappearing at night seems characteristic of dinos, I would definitely get a nitrate and phosphate test kit to monitor your nutrients

TheNewClownFish · 2026-10-06T13:05:36-0400

Thanks for your help guys. I’ll post my light schedule. I bought a used AI prime (non HD).

I don’t have any test kits aside ammonia so I’ll buy that first thing. I’m afraid that it might be Dino’s too because I saw stringy bubbles on my rock but those went away. Should I slow down on my 20% weekly water changes? I’ll buy those test kits right away.

Saltyreef · 2026-10-06T13:59:46-0400

Looks like you started your tank with dry rock. You have very little to no micro fauna that helps stabilize a reef tank.
My dry rock took nearly 2 years to mature and algae outbreaks/nutrients to stabilize. I did not buy any coral in that time but focused on seeding with TSB rubble, pods and other micro fauna. Most of the coral that was trasfered to the tank from an old system died with exception of some basic hardy things like kenya tree. Dry rock tanks take a LONG time to mature vs a tank started with established live rock and live sand.

TheNewClownFish · 2026-10-06T17:36:42-0400

Saltyreef said:
Looks like you started your tank with dry rock. You have very little to no micro fauna that helps stabilize a reef tank.
My dry rock took nearly 2 years to mature and algae outbreaks/nutrients to stabilize. I did not buy any coral in that time but focused on seeding with TSB rubble, pods and other micro fauna. Most of the coral that was trasfered to the tank from an old system died with exception of some basic hardy things like kenya tree. Dry rock tanks take a LONG time to mature vs a tank started with established live rock and live sand.

Ah thanks. Yeah I add tigger pods 2-3 weeks ago. I now see a LOT of pods in my tank. But I'm definitely slowing down on corals. GSP is doing fine, and I might add a Kenya Tree once I fix these issues. Do you think my light schedule seems ok?