Recently, I noticed that the return pump flow had become noticeably weaker than when the tank was first set up.
At first, the water surface would still move even without the powerhead running.
But whenever I turned the powerhead off for cleaning or a water change, that surface movement kept getting weaker. At this point, it barely moved at all.
I already had a powerhead in the tank, so part of me wondered if the basic water movement was still enough.
During the water change, though, I looked at how quickly water was coming from the sump back into the display, and that changed my mind.
This was not just a small drop in flow that I could ignore.
The problem seemed to be on the return pump side.
I am not especially handy, and the return pump I use is not an expensive piece of equipment, so at first I was thinking about just buying a new one.
Still, I decided to at least try taking it out once.
I could not say for sure why the flow had dropped, but I had solved a similar issue with a powerhead by cleaning it before. At minimum, the return pump needed to be checked and cleaned.
The best timing seemed to be during a water change.
Right when I worked up the nerve to pull the return pump out, I ran into a problem.
The two outlets from the rear sump into the display, and the two parts that looked like pipes or hoses, did not come loose as easily as I expected.
I did not want to force anything and break it, so I did not fully remove the pump this time.
It was frustrating. I had finally decided to take the pump apart and clean it, but I got stuck at a part I had not expected.
Was there another option? Was there at least a temporary way to improve the flow?
If an internal part of the pump was broken, or if the broken part was something I could not disassemble, there would not be much I could do. But if debris or algae was blocking the intake, maybe cleaning that area would be enough.
So I checked it right away.
That was a shock. Algae was covering the intake. The return chamber barely gets any light, so I still do not know how algae managed to grow that much there.
Seeing that made me want to pull the whole pump out even more and clean it properly.
But the outlets and piping were still too firmly attached, so I decided to leave the full disassembly for later.
It was summer, but I was also worried that leaving the tank drained for too long could drop the water temperature and stress the livestock.
For now, I did what I could.
Using a pipette, I pulled out some of the algae stuck around the return pump intake.
I do not know exactly what kind of algae it was, but I could see material sitting around the intake, so I removed what I could reach.
After that, the flow definitely felt like it had come back.
Even without the powerhead, the water surface moved a little again, and the corals showed a bit of movement too.
Still, when I put my hand near the outlet, it seemed weaker than it was at the original setup. I will probably need to fully remove the pump at some point.
Algae already bothers me because of how it looks, and sometimes it even covers corals. After this, I disliked it even more.
It even made me wonder if I should keep snails in the return chamber too.
The clownfish, unaware of all this, hides behind the torch coral every time I do a water change.
The water looks clear, but why are there days when corals stay a little less open than usual, or livestock behave differently?
While keeping a 45-cube reef tank, the most frustrating moments were probably when I couldn't figure out the cause of what was happening in the tank.
Dealing with hitchhikers, deciding on a water change schedule, and dealing with algae growth are all difficult, but for me, the hardest part was the time when I had to guess at the reason corals or other livestock were doing poorly.
The tank back when the globe polyps and bubble coral were growing healthily.
For about a year after starting the 45-cube tank, I was watching the tank's condition with my eyes and my gut. Temperature and salinity are relatively simple. They're easy to measure, and you can immediately understand why they matter without anyone explaining it to you.
But I kept wondering whether the values people commonly call water parameters really needed to be measured at all. Each one needed its own test kit, and the testing methods looked more difficult than temperature or salinity, so I kept putting it off.
Then something happened. I did a water change at the same time and in the same way as usual, but after the water change, white spots started appearing on the fish, the tips of the globe polyps that used to open fully no longer opened, and brown algae gradually started covering the globe polyps.
I especially knew something was wrong when Nemo, who had been eating well and breathing normally, stopped eating and started breathing harder and harder.
I searched online. Since I kept seeing people say to do a water change if something seemed wrong, I started doing a water change once a day, and thinking the corals might be lacking oxygen, I hurriedly bought an airstone and added bubbles too.
With the airstone running and daily water changes, things seemed to improve a little. Then, when I looked at the tank after work with a nervous feeling, I saw a dead fish. Not long after that, the globe polyps died too.
After that, the bubble coral, the yellow tang, and the coral I called the bouquet coral suddenly started doing poorly too, and then were gone.
It was really painful. And I kept wondering what on earth was wrong. I had done the water change the way I usually did, so was the problem with the water change? Or was it something else?
I remembered water testing, which I had felt wasn't really necessary. If I had tested the water, would I have been able to figure out what the problem was?
I decided to start measuring the water. I wanted to figure out what absolutely needed to be checked in a tank where I keep corals and fish together, so from that point I looked a little more into individual parameters and decided to measure four high-priority ones.
The four I decided to measure
KH/Alk and Ca are closer to the side that helps corals build skeletons and stay stable. NO3 and PO4 are closer to the nutrient side connected to food, waste, filtration, and algae.
Simply put, one is the flow corals use, and the other is the flow that stays in the tank and builds up there.
KH/Alk: alkalinity connected to pH buffering and coral skeleton formation
Ca: calcium that LPS and stony corals use to build calcium carbonate skeletons
NO3: nitrate left behind after food, waste, and biological filtration
PO4: phosphate connected to food, organic matter, and even the storage capacity of rock and sand
I wrote up separate notes about actually running each test.
Salifert KH/Alk test instructions
Salifert Ca calcium test instructions
Salifert NO3 nitrate test instructions
Salifert PO4 phosphate test instructions
KH/Alk: the buffering strength corals rely on
The reason I looked at KH/Alk first was that I felt it was directly tied to coral response. KH is not pH itself, but alkalinity, which shows how well the water can resist shifts toward the acidic side.
LPS like torch coral and Acan coral show water changes very clearly. When the polyps open less or the tissue looks shrunken, I can't say for sure that there's only one cause, but it is worth checking whether KH is swinging.
When I first measured it, the value came out around 12.8 to 13.1 dKH, which was clearly higher than the commonly known 8 to 12 dKH range.
Based on that value, I formed a hypothesis that the KH of the new water made for a 25% water change once a week was staying higher than what the corals were consuming, and that this repeated pattern was pushing the value up.
After reducing the water change amount and testing for a month, the KH value actually moved into the normal range.
Ca: the material corals use to build skeletons
Ca is the main material in a coral skeleton. Even though LPS look fleshy and full, they still have a hard skeleton inside, and when they form new heads or thicken their skeleton, they use Ca and KH together.
The most disappointing one was the bubble coral. The once-full bubble coral slowly separated between the skeleton and the polyp tissue over a very long period of time, until it finally separated completely. I think I might have made a better judgment if I had tracked that value.
NO3: the residue left after processing food
NO3 is nitrate left after food, waste, and dead organic matter go through bacterial processes.
High NO3 doesn't immediately mean disaster, but if it stays high for a long time, it can be linked to increased algae growth or changes in coral color. On the other hand, it doesn't have to be zero either. Corals, symbiotic algae, and bacterial ecosystems also need some nitrogen source.
PO4: a value that can affect both algae and coral growth
PO4 is phosphate. People often associate it with algae, but phosphorus is also a nutrient needed for life.
The problem is that the tank can become unstable whether it is too low or too high. If it's too low, the balance between corals and microbes can be disrupted, and if it's too high, it can be linked to glass algae, rock algae, and cyanobacteria.
Moving from gut feeling to records
Of course, not all symptoms that appeared in the livestock could have been found or prevented through testing.
Still, it felt too frustrating to keep relying on gut feeling alone, and once I started measuring, at least I no longer looked at everything purely by instinct like before.
I now had a reference point for seeing how the measured values were moving behind the visible changes, like whether the water looked clear, whether the corals were open, or whether algae was increasing.
I pulled out the Salifert Ca test kit to check the calcium level in the tank.
The kit comes with a test vial, a 2 ml syringe, a 1 ml syringe, a plastic tip, the Ca-1 powder reagent, the Ca-2 liquid reagent, a special spoon, a chart, and the instructions.
Here is a quick summary of the testing steps.
1. Put 2 ml of tank water into the test vial.
Draw 2 ml of water. Try to pull it up as cleanly as possible, with as little foam as possible.
When dispensing the water from the syringe into the vial, do it gently and slowly so it does not splash against the vial walls.
2. Add one spoonful of the Ca-1 powder reagent with the special spoon.
As with other test kits, fill the spoon generously first, then gently tap it with your finger so the spoon ends up full.
3. Gently mix the vial for about 5 seconds.
The instructions do not specifically say to mix, but if you do not, the Ca-1 powder remains in the water, so I gave it a quick mix.
4. Draw the Ca-2 solution into the syringe up to the black tip at 1 ml.
Check that the pink plastic tip is seated firmly.Set it to 1 ml based on the black tip. The solution does not need to reach 1 ml exactly.
After firmly attaching the plastic tip to the 1 ml syringe, draw the Ca-2 reagent up to the 1.00 ml mark. At this point, align the lower reference line of the black rubber piston with 1.00 ml.
It was written in the instructions, but at first I was not sure whether the reference was the solution level or the tip, so I searched it and confirmed that, as shown in the photo, you line up the end of the black tip with 1.00 ml.
5. Mix 0.6 ml of Ca-2 reagent into the water.
With the syringe set to 1.00 ml, add 0.6 ml into the vial. The black tip of the syringe will then line up at 0.4 ml, and the liquid in the vial will turn pink.
6. Add the Ca-2 reagent drop by drop, swirling for about 1 to 2 seconds each time.
Keep going slowly until the color changes from pink to blue. When it starts looking purple in the middle, it feels like you are very close to the end, so from that point on I had to be more careful and watch it one drop at a time.
Like with the KH/Alk test, you need to watch the point where the solution changes color, and this time too I needed to record the exact moment the color clearly changed.
I thought video would make it clearer, so I recorded one. You can clearly see the color change.
Once the color turns blue, hold the syringe with the tip facing up and compare the position of the black rubber piston with the chart to read the tank's Ca level.
Based on the photo above, the black mark looks to be around 0.19, which puts the result at about 405, between 0.18 and 0.20 on the chart.
This reading
This Ca reading looked to be around 405 ppm.
As with other Salifert kits, this is not a digital measurement, so the result may be a little different from the actual value, but it still seems important to measure it the same way each time so you can keep track of the number.
Before starting the blog, I kept wondering if I was just taking on more work when I already didn’t have much time. Could I really do this properly? I was already worried about starting a blog when I’m not even that good at writing.
Still, I had been wanting to write better for a while. I also wanted to leave some thoughts in writing about the aquarium that became a new part of life after getting married. And I felt like it was too wasteful to keep thinking about it and do nothing, so I just started.
Fortunately, after running the blog for a week, I’m enjoying the process itself, almost like I’ve started a new hobby.
What I didn’t expect was that some unexpected questions would come up along the way.
It took longer than I expected to write and edit.
I never thought I’d be worrying about SEO while writing.
What surprised me most was that polishing and revising the draft took longer than writing it in the first place. I honestly thought a quick round of editing after the draft would be enough.
Once I finished a post and was about to publish it, I found myself checking whether the title was too stiff, whether the slug looked strange, whether it was written the way the Yoast SEO plugin suggested, and so on…
Even so, I didn’t dislike the process. It feels like I’m slowly touching up a space that’s mine, which is annoying but strangely fun. As I keep writing, I’m also getting more of a desire to do better, so I’ve been pulling out some books on writing that I read before and revisiting them during my commute.
I decided not to push too hard
The first time I’ve used Canva since my college days. I don’t think it used to do video editing, but now it does.
I said I would keep things very light, but I’ve already made and started using an English version, an image optimization tool, a draft-writing tool, and an editing tool.
I’ve even tried video editing, something I’d never done before. It’s just cut editing and adding music, but still. I uploaded it to YouTube, made a Threads account, and linked my blog posts there too. I’m already doing quite a bit.
I’ve had more than a few projects that started with too much energy and then fell apart as I lost steam, so when I feel myself overdoing it, I think it would help to remember the purpose of writing about my aquarium and reset my direction like this once a week.
I thought there would be no visitors at all
Google Analytics. There were more visitors than I expected. A real-time visitor showed up while I was writing. Thank you!
At first, I honestly thought there would be zero visitors except for family and acquaintances, but strangely enough, about one person a day comes in through search.
What was especially fun was that, since I was also posting in English, people came from the U.S., Poland, Canada, and elsewhere. Thank you!
But there were more hacking attempts.
There are far more malicious visits than real visitors.
Lately the attacks seem to have dropped a bit, maybe because they were blocked and moved on to other targets, but brute-force attempts are still coming in.
But even that is kind of funny. Even if it isn’t a person, someone is still finding this place!
Next week
Next week, I’m planning to organize some aquarium photos, finish the Salifert post, and pull out records on the tank livestock one by one.
To wrap up, the cute clownfish hiding behind the torch coral during the water change
The Nemo I keep now really likes the torch coral. Its name is Jamo, short for “wild Nemo” in Korean.
Jamo is almost always rubbing against the torch like this. Watching the torch coral tentacles sway while Jamo keeps nestling into them has become one of the small joys of keeping the tank.
A guest was over, and while we were talking about the tank, I mentioned that when the flow pump turns off, the torch coral tentacles freeze in place as if they had been struck by lightning. They were curious, so I turned the flow pump off for a moment.
As soon as the water flow stopped, the torch coral tentacles barely moved, and Nemo stopped too. The way it looked confused, almost like a little fish that had suddenly lost its home, was both cute and funny.
I pulled out the Salifert NO3 test kit to check nitrate in the reef tank.
The kit itself is simple: a test vial, 1 ml syringe, NO3-1 liquid reagent, NO3-2 powder reagent, the supplied spoon, color chart, and instructions.
The basic test process is:
1. Add 1 ml of tank water to the test vial.
At this point, I try to draw the sample with as few bubbles as possible.
2. Add 4 drops of NO3-1 liquid reagent.
3. Add one level spoon of NO3-2 powder reagent.
According to the instructions, the spoon should be filled and then leveled off.
When scooping the powder, it can be a little too full or a little short. I found it easiest to scoop a bit generously and gently tap off the excess so it sits level with the spoon.
4. Mix gently for 30 seconds, then wait 3 minutes.
Since the test uses a powder reagent, I felt better timing the mixing instead of just giving it a quick swirl and moving on.
5. Read the Salifert NO3 test from above on the white area of the color chart.
The part I found most confusing in the Salifert NO3 test was how to read the color chart.
The basic method is to place the test vial on the white area of the color chart and compare the color while looking down from above.
The instructions also say to compare the color in diffuse natural light. Under blue reef lighting, the color can look different.
It would be nice if the color landed on one exact block, but in practice it often looks like it sits between two colors. In that case, I record it as a middle value instead of forcing it into one number.
While waiting for the 3-minute mark, I wondered whether I would need to make a new sample if I missed the exact reading time.
So I compared the color at the 3-minute mark with the color after roughly 30 minutes.
The left one is the first reading. The right one is after 30 minutes.
To my eyes, the value did not seem to change much. I did not compare it over several time intervals, but if the sample has been sitting around for a long time, I would rather test again than treat it as a clean reading.
I could not find a clear cutoff in Reef2Reef or other overseas reefing discussions either. Most of what I found came back to the same practical point: read it as close to the 3-minute instruction as possible, and do not rely too much on a sample that has been left out for a long time.
Reading the vial from the side
While checking whether the method I described was right, I also found that the kit can be read from the side.
For that method, hold the test vial upright, place the white part of the color chart behind the vial, and look through it from the side.
Because the color looks stronger from the side, the number on the chart should not be recorded as-is. It needs to be divided by 10.
For example, if the side view looks close to the 50 ppm color, I would record the result as about 5 ppm.
For normal use, I would use the top-down reading first, then use the side view only as a supporting method when the value is hard to judge.
This test result
This NO3 reading looks like it falls somewhere between 10 and 25 ppm, roughly 15-20 ppm by eye.
I took out the Salifert test kit to check the KH/Alk in my 45 cm cube reef tank.
The kit is simple: a test vial, KH-Ind reagent, KH reagent, a 1 ml syringe, a plastic tip, and the instruction sheet.
The test itself is simple, but the details were much more confusing: where to line up the 1 ml syringe mark, and exactly where to count the color-change endpoint.
To summarize the test method:
1. Add 4 ml of tank water to the test vial.
Try to keep bubbles out as much as possible here.
2. Add 4 drops of KH-Ind reagent and gently swirl for 5 seconds.
3. Fill the syringe with 1 ml of KH reagent.
At this point, make sure the tip is tightly attached to the syringe.
The part that confused me most at first was drawing the KH reagent into the 1 ml syringe.
I thought the liquid itself had to come up to the 1 ml mark, but it should be aligned by the black rubber piston, not the liquid level.
If you pull more reagent to make the liquid surface line up with 1 ml, you can end up using more reagent than the instruction sheet assumes, and the result can be thrown off.
Always line up 1 ml by the black piston, like in the photo on the right.
4. Add one drop, swirl for 2 seconds, and repeat until you reach the color-change point.
First color-change point The color is ambiguousOne more drop added: the solution is clearly reddish.
Another confusing point was exactly where to count the color change.
At first the solution looks blue or greenish; as you add the KH reagent one drop at a time, it gradually moves toward orange, pink, and red tones.
According to the instruction sheet, the endpoint is the first point where the color changes to an orange, red, or pink tone.
But there was a moment where the first visible change looked ambiguous, almost like 50% blue and 50% red.
At that point I was not sure whether to stop right away or add one more drop.
After looking it up, I decided that if the color still looks half-and-half, I would treat it as an intermediate stage and add one more drop.
Then, after swirling for about 1-2 seconds, I treat the first moment when orange, pink, or red is clearly dominant overall as the measurement point.
I do not wait until it becomes a deep red.
Swirl well after every drop.
View it against a white background.
If blue/green is still the main color, add one more drop.
Stop at the first point where red tones are dominant overall.
5. Read the syringe mark and check the KH/Alk value in the chart.
This Measurement
The KH/Alk reading this time came out around 9.6 dKH.
Since the black piston on the syringe was around the 0.38 mark, I just found that value in the chart and checked it.
