My first saltwater tank - Aqueon Frameless Cube Aquarium, 3 Gallon

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I'm using a pH meter device along with liquid API test. I use both on all 6 of my aquariums. Low pH seems to be the issue since the hard corals I had in there pretty much melted away and the soft Kenya Tree coral isn't doing well at all.

I've tried using the Seachem reef buffer and brought up the pH but it always falls back down and stays there.

When I first started I was using Imagitarium Pacific Ocean Water but have since started mixing my own water using Instant Ocean reef crystals.
Does the pH meter get calibrated regularly?

Is there much aeration/ surface turbulence in the tank?
it might be a build up of carbon dioxide that is dropping the pH. Increasing aeration/ surface turbulence for a week should prove that one way or another.
No, it's a pretty new device. And, I think it's working ok since the readings for API tests and it are close. And the fact that the corals aren't doing good I think is a good indication that pH could be the problem. Yes, I have the output for the filter at the top of the water and it flows across the top. There is a small section of the top of the water, near the back, that the flow doesn't touch because the light brace is there. Does it look good to you in the video? I can up the speed if it's needed. I was worried about too much current on the corals at the higher speed.

I've also turned off the light and closed window shades for the time being. There's a small amount of indirect light hitting the tank at this time.

I just did a liquid test and it is showing 8.4 pH. Does that look like 8.4 pH to you? The device is showing like a 7.5 pH so perhaps I do need to recalibrate it. It's a cheap device anyways prob not worth relying on. It was at one time in line with the liquid tests though.

So, not sure what else to do though. If I get a sump with refugium wouldn't that help with the algae issue?

One thought is there's just way too much light. That's why I'm trying no lights right now.
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Also, here are results from API liquid test just took. Salinity measured with refractometer.

Salinity 36 ppt
pH 8.4
Calcium 440 ppm
KH 10 dKH
Most corals that live near the surface will suffer without light. I would be concerned about them not having light for more than 24-48 hours.

A refugium will give you more water volume and that can help stabilise the conditions in the tank, but it won't make any difference to algae unless you have high nitrates or phosphates. Then the macro algae in the refugium will help keep those levels down and minimise algae. Because corals have a symbiotic algae living in their cells, they photosynthesise when they get light and help use some nutrients produced by the coral animal and in the water. They should also reduce the light getting to the rocks and substrate (by shading) and help limit algae in those areas.

Diatoms are slightly different and regularly grow in newly set up aquariums. After a few months they normally die off and get replaced by normal types of algae.

You can grow macro algae in coral tanks. I used to have feather Caulerpa, bubble Caulerpa and Halimeda in my tanks. Just don't let it crawl across the corals. A friend of mine used to grow turtle grass in his marine tank. Any macro algae you can get to grow in the tank will help reduce nutrients and minimise algae growth.

When dealing with marine algae, make sure the temperature or salinity doesn't fluctuate or change suddenly because it can kill them. If you buy some from a shop, make sure your tank has the same temperature and salinity and keep the plants out of the sun while travelling home.


The liquid pH test does look like it's around 8.4, which is fine.

The salinity (specific gravity) could come down a little bit to 35ppt. Having it at 36ppt isn't a big issue but dropping it a fraction might help some corals depending on what the shop's water was before you got them, and where they originated from.


There should be enough surface turbulence to keep oxygen levels up but you can increase it a bit if you like. Some corals like lots of water movement and others prefer less. Try increasing and decreasing a bit and see how it affects the corals.

You can drill a few more holes in the spray bar (filter outlet) so more water can come out. If you don't want to drill into the current spray bar, buy a piece of pvc pipe from a hardware store that fits on the filter and drill holes in that.
Thanks. I've done a little surgery on the Kenya Tree tonight. By that I mean I cleaned off the green algae on it (mostly by using a turkey baster like instrument) and there was some black buildup spots on it that I was able to easliy scrap off, in a gentle fashion. There's still some black spots and I'll try to get those off later. I didn't want to mess with it too much. Some of the branches were also really small and black so I trimed them off. I will try turning on the light with a low setting tommorow and see how it does. It seems like the green algae built up even with the lights off though so hopefully it won't get to be too much. I'll try increasing the water flow too, and cleaning out the output holes because they used to all flow the same amount and some don't look like.
Algae that grows when the lights are off is usually blue green algae (Cyanobacter bacteria). This is a photosynthetic bacteria that comes in a range of colours including green, blue, black, red, brown and pink. It loves nutrients, red light, low oxygen levels and slow moving water.

Try to have a light that produces a 5500-6500K wavelength.
Increasing water movement can help.
Reducing nutrients, especially dry foods, can help get rid of it.

If it still won't go, you can use a product like Ultralife Blue Green Slime Stain Remover.
I'm having a go at another coral frag. The smaller frags I've tried are cheap so not a big loss. The Kenya Tree costed a bit more so sorry to see how it is doing. It's still looking pretty sad but I'm being patient to see if it will turn around. My pH has been at a stable 8 ppm since I last reported and I haven't done anything special to help it, other then the kalkwasser I put in the top off water.

I'm also more carefully monitoring calcium and dosing it as needed.

This one is a Montipora.


I'm also trying different light settings and times. This is my current settings. No light on in the morning for the most part. There is still ambient outside light from nearby windows but not direct. Algae is still present but under control.


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You have blue green algae in the sand. The dark green stuff under the sand against the glass is Cyanobacteria. The light green patches on the sand look like Cyanobacteria too.

I would have equal parts red, blue white light for a couple of weeks and see if it helps
You have blue green algae in the sand. The dark green stuff under the sand against the glass is Cyanobacteria. The light green patches on the sand look like Cyanobacteria too.

I would have equal parts red, blue white light for a couple of weeks and see if it helps
Thanks. I was curiuos so did a quick search on the Internet to see what the difference was betwen blue-green algae and cyanobacteria. The first few results I looked over says they are the same thing.
Blue green algae are Cyanobacter bacteria. Cyanobacteria is the scientific name for them, blue green algae is the common name.

They come in a variety of colours ranging from light to dark green, dark blue, brown, black, purple, pink and red. They are an ancient group that were around before fish or dinosaurs or virtually everything else, and were the things that created the oxygen we breath today. Unfortunately they can be a pain to get rid of in an aquarium. Clean water, lots of oxygen and water movement and decent light help limit their growth, as does reducing nutrients. It can also grow in a clean newly set up tank and normally dies off when the tank has stabilised after 3-6 months.

As a last resort, this stuff can kill it.
The colors are so much more vibrant in person. I heard LEDs aren't the best for photos so I'm thinking that's why these don't show all the detail. I'm using an orange coral lense on my phone cam for this pic.
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This pic came out pretty good. Using an orange lens from reef glasses.
The new frag is doing well and is growing.


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