Help me clean up my Fluval Evo 13.5

austenreefer · Jul 9, 2025

Context: I have been in the hobby now for 5+ years. I have had tanks up to 65 gallons, but for a while we lived in a condo so I went back down to a Fluval Evo 13.5 (the tank that started it all ironically) and in all honesty everything in the tank is doing fine, but it just get so much dang algae growth, both on the glass and on the rocks. Feels like I do a big water change and clean it and make it look nice just for it to be back to looking bad again a week later.... I don't do water changes as much as I should I will admit, but some of these rocks are very old and the tank itself is probably 2+ years old at this point so I wouldn't think the lack of weekly water changes is what's doing it. Wanna fall in love with reefing again and not just go through the motions and it feeling like a chore. Here is what the tank has and what I am thinking of doing to bring it back, let me know if you would do anything different:

Current tank:
- One clownfish (other one jumped about a year ago and I never put a new one in because the one that is in there is pretty mean)
- Maybe a handful of crabs, not many
- All soft corals (one huge toadstool leather the size of my head just about, GSP, a few zoas scattered about)
- Radion XR15 G5 Pro (turned down to 20%)
- SICCE Syncra Silent 1.0 w/ random flow generators from Etsy
- Seachem Purigen / Phosguard in chamber 2
- Auto feeding pellets
- ATO

Potential Changes:
- Making a DIY media basket for chamber 1, adding bonded filter floss, chemipure blue, and poly-fill to the 3 chambers
- Buying a Hydor Koralia Nano Aquarium Circulation Pump - 240GPH (The SICCE is a great pump but still feels like the tank needs more flow, probably because the toadstool is so big it blocks a lot of flow from the random flow generators)
- Revamped clean up crew. Not exactly sure what the composition should be, usually I do 10 $1 snails, and 10 $1 crabs but I am open to suggestions of specifics

Bonus: if I am able to fix all these issues I might reward myself with adding something new to the tank. Again I'm not sure another clown is a good idea since it took me 3 tries to get her one she liked and it ended up jumping. So suggestions on that too would be cool.

I'm not home right now but if pictures / water tests would be helpful let me know I think I still have most of them in a box somewhere I can pull them out and test.

Uncle99 · Jul 9, 2025

I can’t see any posted parameters in terms of water chemistry which is the cause of much of the pest stuff.

What are these and what is the daily flux

austenreefer · Jul 9, 2025

Uncle99 said:
I can’t see any posted parameters in terms of water chemistry which is the cause of much of the pest stuff.

What are these and what is the daily flux

Nitrates are less than 0.05 but I assume that’s the algae’s doing. I have a phosphate test kit but must’ve lost the dropper in the last move. Gotta order a new one

Mr. Mojo Rising · Jul 9, 2025

An extra powerhead will certainly help, to keep detritus suspended and push it into the filtration system. How often does the auto feeder feed the one fish? I usually have algae problems after using the auto feeder for vacations, I would assume that uneaten pellets are feeding the algae.

austenreefer · Jul 9, 2025

Mr. Mojo Rising said:
An extra powerhead will certainly help, to keep detritus suspended and push it into the filtration system. How often does the auto feeder feed the one fish? I usually have algae problems after using the auto feeder for vacations, I would assume that uneaten pellets are feeding the algae.

It goes off 3 times a day on the smallest opening. Just a few pellets each time

Uncle99 · Jul 9, 2025

austenreefer said:
Nitrates are less than 0.05 but I assume that’s the algae’s doing. I have a phosphate test kit but must’ve lost the dropper in the last move. Gotta order a new one

Phosphate feeds algae growth along with light.
Too much or virtually none brings pest stuff.

The only tool that ever gave me a good read on phosphate was the Hanna, phosphorus checker.

Biokabe · Jul 9, 2025

Since you've been in the hobby for a while, I'll give you the benefit of the doubt and assume that you're already using RO/DI, 0 TDS water as your baseline. If not, address that first of all.

With that out of the way, there are three easy and obvious steps to take to begin with.

First, you need to get on a consistent water change schedule. 4-6 gallons a week will do wonders for a tank your size. Doesn't have to be 7 days on the nose, but every 7-10 days is a good goal to shoot for. If doing water changes is a pain, ask yourself why that is and take steps to make it less of a pain. Water changes aren't magical (with a well-balanced reef you can skip them entirely), but if things are ugly that's the first and most effective thing to establish.

Second, bump up your CUC. Imagine, for a second, that your tank had nothing but rocks, sand and algae in it. If you fed your tank, where would the nutrition go? Into the algae, of course. Now, add a fish to the tank. When you feed the tank, where does the nutrition go? Some of it still goes into the algae, but some of it also goes into your fish, and is used to make your fish bigger. Carry the thought on: If you have more CUC, then when you feed the tank, that's more places for the nutrition to go that isn't algae.

Don't focus on the $ value of the CUC. You're not buying a $1 snail; you're buying a cerith snail, an astrea snail, or a nassarius snail. Each CUC member will do different things for your tank. You need CUC members that will attack all aspects of keeping your tank clean: Film algae, detritus, leftover food, hair algae, etc. A good blend of CUC is essential. Reefcleaners.org is a great resource for CUC. If you haven't used him before, the website is a little old-school but the information and service is top-notch. Spend some time reading over the various critters he sells and pick out a good mix. Don't just focus on algae eaters - scavengers and detrivores are, in some ways, more important than those who directly eat algae, because they prevent nutrition from getting to the algae to begin with.

Third, improve the flow in your tank. Flow keeps particles and detritus suspended, which makes it more difficult for algae to access the nutrients contained within. This also gives your mechanical and chemical filtration more opportunities to filter the excess nutrients out of the water.

There are other things that you can do as well, but with the limited footprint of a 13.5 Evo I'm not sure how realistic they are. I've always found an ATS (algae turf scrubber) to be very effective at controlling algae in the display, but getting one properly sized for such a small tank while still being effective is a tough ask. Same thing with a protein skimmer.

Other than that - keep pulling up any algae that you can easily rip off. Plenty of critters will eat hair algae when it's short, but very few will touch it if it's long.