Hello all, sorry for jumping in with a problem looking for answers. Never been much of a forum guy so not sure about the normal forum etiquette so please bear with me. I'm getting a bit desperate now and trying to ask around different forums for help.
I have a 145L tank freshwater tropical tank that has been going for a couple of years now, hosting a variety of plants and fish (half a dozen small tetra, a couple of guppies, a loaches, platies and a dwarf gourami) with a few drift wood and rocks as decors. T5 light comes on during the evening, enough to keep the plants going but algae had never been much of a problem. The odd bouts of algae from time to time but never enough to concern me, and all was running well until I failed to quarantine a new plant that I bought. It started off with a light dusting of green algae on front glass panel of the tank.
Almost overnight (well, not literally but you know what I mean) a sheets of green stuff was covering the hardscape, broad leaf plants, sand, wood, stones, everything.

I thought it was just an algae outbreak which I could deal with. I checked the levels, ammonia and nitrites were zero, phosphate and nitrates were low on API scale.

I did more water change than usual (every week instead of two weekly) and manually removed the algae as much as I could but the dreaded thing just kept coming back faster than I could remove them.
I then bought a team of shrimps and snails hoping they'd eat it but they wouldn't even go near it. Some of the fish (guppies) did have a nibble every so often but nowhere near enough to keep it under control. It might have been just my imagination but the fish were getting lazy and less active. They're not gasping for air, but some of them were just hovering round the top a lot more.

Slowly the more delicate plants started to die off. Lost a few fish in quick succession and I began to panic. Used a number of algae removers but none did anything other than burning a hole in my pocket.

After lots of searching on the net and looking at pictures I then realised that it's blue-green algae (cyanobacteria) that I have in the tank. So immediately I used an extra pump to increase the flow, cut down feed for the fish, turn the lights off (T5) and even used RO water for water change to get the phosphate down. True enough it slowed it right down. The trouble is as soon as I have any lights on, the dreaded thing comes back with a vengeance.

I tried the Ultra Life Blue Green Algae remover which seemed to have worked initially (never completely gone) but just as I thought it was safe to restock it returned a few weeks after. I'm now at a loss as to what to do. I've seen someone mentioning using hydrogen peroxide but from the sound of it, it's a bit tricky to get right.

I also read somewhere that Erythromycin can work (is that the same as what you get from your doctor when you have a chest infection??), although the risk of wiping out all the good bacteria is a bit worrying. Does anyone even know where I can get the treatment (specifically for freshwater aquarium) from? Don't seem to find it anywhere, not on the net, not in LFS, not even eBay.

I'm now afraid to restock any plants or fish until it is under control, and I don't want to keep the tank permanently in the dark.

Can anyone here help?

Hi

You won't find erythromycin in the UK as it's an anti-biotic and is prescription only. You might get a vet to prescribe it, but finding one who'd know the right dosage for this problem may be difficult. It does run the risk of killing your beneficial bacteria as well.

I've been fighting cyano in one of my tanks and what worked for me was to do a very large water change, syphoning out as much cyano as possible then dose with Boyd's Chemiclean (running a large airstone with this is essential). After 48 hours I did another large water change and syphoned any remaining cyano out followed by a second dose of Chemiclean and a 20% water change 48 hours later.

Hi, thanks for the info.

At the moment I'm keeping a lid on it by weekly 2 hrs cleanig routine bacause it grows bacxk so quickly I'm having to clean the tank weekly. Syphoning the substrates, peeling off what I can, then full filter and water change. Followed by episodes depression after watching more plants +/- fish dying. I hardly have the ligfhts on more than a few hrs a day now because it's just not pleasant to look at.

Did try Ultralife Blue green algae remover (which I beleive is same or similar to Chemiclean?) which only gave temprory releive.

Had a look on eBay and searched for blue green algae remover, hoping to find the erythromycin there, no luck, and have sionce ruled out the idea of using Erythromycin. But I noticed another remover other than UltraLife one. It's called PureBlue. Not seen it before but looks promising though, has anyone tried or know about it?

If fish are dying there's something else in play here as bga shouldn't be causing fish deaths. What are your tests showing?

Readings seems to be ok, Ammonia and nitrite are zero, phosphate and nitrates are both low on API scale. Temp is the same as ever, nothing else as changed. Is there anything else I need to be testing?

The thing that foxed me most is that the system worked really well and was well established for a couple of years, lots of plants, a low fish stock and 2 weekly water change. The only thing I could think of that changed was a plant I bought just before and didn't think of quarantine it before hand. Less than a week later the problem started.

I have an external filter with 1000L/H pump, and in the filter there are 3 trays, one for foam mesh, one for carbon and one for Rawphos. Water goes through a U/V steriliser (that I added after the problem started, didn't help but I kept it going anyway). I've also since added a couple of powerheads to prevent any stagnant area.

Light wise just a couple of T5 that came with the aquarium, tubes have just been changed a few months back so not really old.

Fish wise I have half a dozen small tetra, a couple of guppies, a loaches, a platies and a dwarf gourami, now I've lost the guppies and the loaches since the problem started and have not restocked. So I don't think that's over stocked???

As far as substrate is concerned, mainly sand, a couple of pieces of drift wood and some rocks, and that's been the same since the beginning. Fair bit of plants and I don't add any fertiliser or anything for the plants routinely.

So a relatively low maintenance tank really, and hadn't needed to do much other than water and filter change and the odd bit of cleaning every so often.

Normally use tap water, treated obviously, for water change. When I test the tap water, nitrate and phosphate is minimum on API scale. Tried using RO water I bought from LFS for water change but gave up after a month, not making and difference and cost a fortune.

Now this green muck started destroying everything. A lot of the more delicate plants are dead, lost a few fish, and the tank looks more like a sewage treatment plant.

Is there something I'm missing? Already tried the UltraLife BlueGreen algae remover with no success, I might just give this PureBlue I saw on eBay a try, unless you think there's something else I could be doing first?

You're not overstocked. It may be that your nitrate is too low. That's been the cause in my tank. Where there is too little nitrate in the tank, plants can't grow effectively (hence the die-off), but cyanobacteria can take hold because it can fix atmospheric nitrogen and make use of the other nutrients in the water. This may be why you can clear it with treatments, but it keeps coming back. I would repeat the treatment (either the balck out or Chemiclean/Ultra-Life. Suck out all the cyano you can see and then dose a plant fertiliser that includes nitrates and see if that stops it returning.

Thanks, I'll give that a go. Do you think the increased water change was getting rid of nitrates too much? So I need to get rid of all nutrients by water change and then replace the nitrates for plants. I'll give that a go, meanwhile I'll get some treatment. Might just give ths PureBlue I saw on eBay a go.

Got the PureBlue blue-green algae remover this morning, which is pretty quick considering I only ordered it just before the weekend!
As for the tank, only cleaned it a few days ago and is already half covered in the slime. Didn't have time to deal with it this morning so had to wait till I got back from work.
As per instruction, made up the solution with the powder provided and put in the amount according to my tank size, pretty straight forward really. So far so good.
I tried to ask the seller how it works just so I can be sure if the fish is going to be ok, as I wouldn't be able to catch them without causing a great deal of stress to the fish. Understandably they wouldn't give me the ingredient list but reassure me that the fish will be perfectly fine. Anyway, they gave me their website address which has a bit of info on it if you're interested: www.aquamedics.co.uk
I'm going to keep a very close eye on it. I guess the most important thing is to make sure it hasn't wiped out the good bacteria together with the cyanobacteria and practically un-cycled the tank. So I'll be doing check on the ammonia level daily. Is there anything else I need to be keeping an eye on otherwise?
Fingers crossed.

On the fifth day after application of the PureBlue treatment, I was getting quite disappointed this morning, nothing much has changed, the blue-green algae has not got worse since the treatment began but neither had it got any better. So for the whole day at work I was planning how to blitz the tank, and worry about how many of the fish and plants I'll manage to save, and generally getting quite depressed.

Then when I got home from work, like magic fairies have been, the tank was completely cleared of the slime, not a trace of it! So the PureBlue blue-green algae remover has worked! I still can't believe just how sudden it worked, it's like magic, just couldn't beleive it!

I've not seen the tank so clean for a long time! Unfortunately now that the slime has disappeared, it is even more obvious that a lot of the plants had died. Just spent the last hour or so clearing out the dead plants.

I won't get too excited though (difficult since the tank looks so nice now) because it's still early days yet, the slime could potentially come back anytime, I shall see, not that I'm suspecious or anything, you know when threy say it's too good to be true. . . . Really hope the treatment will last, then I can start to think about restocking the tank.

So so happy PureBlue has done the trick! :) :)

Checked all levels daily this whole week, ammonia and nitrite were always zero, nitrate and phosphate went up a bit yesterday, now back to 0.5 and 5 ppm.

I'll carry on keeping a close eye on the levels, and as suggested per instruction, will hold off water change for another week. Will report back next week, or sooner if anything changes.

It's been a few weeks now since the treatment started. I thought I'd post an update.
The treatment worked really quickly, and the result has lasted. Took a little effort to clear away the visibly dead plants and it looked quite bare initially. Few weeks on and the plants are now healthy, fish are happy. I've started re-stocking the plants and slowly added a few fish back in, lights are back on so I'm enjoying the aquarium a lot more now. It's back to normal maintenance routine, levels are stable and there is no sign of the slime returning, so I guess it really has worked, and properly got rid of the slime for good. Just hope it doesn't return, but if it did, I have a spare treatment kept aside so I can treat it before it kills anything in my aquarium. Thank you all for the advice and information, very much appreciated.