how long can you not feed the fish for?

[Rosemary]

Hello!

I'm struggling at the moment with cyano.
13liter tank, 4 pearl danios and one otto and moderate plant load. It started when we moved house and my lights were accidently put onto a longer timer, going from 7hours to 12, at the same time as my DIY CO2 ran out and was not replaced for a few weeks.

So - about 2 weeks ago I reduced the lights to 7hrs, redid the CO2, did two water changes in 4 days, weekly thereafter, and reduced the fish feeding.  I never actually see the fish eat, they're very shy, so it is hard to gauge how much to feed.

But - cyano is not yet abating and comes back pretty quickly after a water change, covering most of the substrate and many plants.

I tried to black out the tank, but with the hot weather the evaporation caused the water to just pour out!

Tyrone you mentioned not feeding fish for a week...the question is how long before the fish starve?! or, for how long can one safely not feed fish in order to reduce algae/cyano?  
 

[R.C.]

Before you start starving your fish to get rid of algae (lol), lets rather take a step back and look at what the root cause of your problem is.  For that we'd need to know a little more about your setup.  First questions that would come to mind are, firstly what kelvin rating are your lamps, secondly are there any visible or excess decomposing organic matter in the tank and thirdly, what are your nitrate readings?

[ghostsword]

I would start by doing daily water changes, 13 liters is not a big tank, so it is easy to do it. Also the weather is getting hotter now, so maybe you should relocate the fish to another container, using the water you have on the tank, give a good rub to everything and after a day or so put the fish back still using the same water, then carry on with water changes.

I had a situation a year ago, while I was in Cape Town for a month, that a filter tube got kinked and when I got back to the UK all my fish were dead, there was muck everywhere, it just smelled of death.

I took the large majority of plants away, turned off the heater and removed the filter, caught up what was floating and bought ghost shrimp, lots of them.

In under a week they cleaned it all, and I got a 120L tank.

For organic matter shrimp are just amazing, they eat it all, so for a small tank, if you can get shrimp in South Africa, that may be a solution.

[Slagter]

I had an issue in my 400L tank before I broke it down. My entire top of the tank was covered with Duckweed, I had stopped regular fertilization and I stopped the Co2 in the tank.

I had a massive amount of Cyano start growing, but because I wasn't going to keep maintaining the tank I just left it. Every now and then I added some of the Tropica plant ferts into the tank, but never on a regular basis. The duckweed had stopped probably 50% of the light from getting to the plants in the tank.

I left the tank. For about a week or 2. The Cyano eventually just vanished. Without me doing anything. The plants in the tank survived this as well. I had, L. aromatica, Rotalas, Crypts, Hygro's, Ammania senegalensis, hairgrass, and some others I can't think of now. They were all covered. And after a week or 2 of letting the Cyano do it's thing, it was gone. In fact most of the algae in the tank disappeared.

So maybe nutrient reduction and lower lighting have something to do with eradicating Cyano?

[shihr]

well in my experiences, the answer to ur original question, i have gone 2wks without feeding my fish.. not that they liked it though but they were well fed b4 the fast..

[R.C.]

Koi kept in a pond will go into a state of near hibernation and live off their fat reserves throughout winter.  In our tropical tanks there may be too many variables for a straight answer, but it’s been said that generally (though debatable) most fish can easily go a month or two without food. 

[Rosemary]

Thanks for all the comments, everyone. Much appreciated.
@ R.C. It's due for a weekly water change tomorrow. A dipstick today shows nitrates about 5mg/l, GH 6, KH 3, pH 6.8. The light is a 13W 7200K clip on light that I got from Liaquat about 5 months ago. However the tank is in an area where it gets quite a lot of natural light, and I've noticed about 20mins of late evening sunlight (6:30pm).
I use Dirk's fertilizer with water changes. There's no significant organic waste - the odd yellowing leaf that gets taken out with water changes - no snails, no dead fish (only 5 and I count them regularly!) The only thing is a 1 month old piece of drift wood that does cause a bit of a tint in the water by the end of the week.

I don't really want to starve my fish...!...but I do think I may be overfeeding them as there are so few, they're very shy and I never, ever see them eat anything.

[tyronegenade]

Danios can go without food for at least 2 weeks without problems. What food are you feeding?

To grow so fast Cyano need both high N and P. NH4+ N is OK for them and with good light they can quickly out compete plants for it but without the P they can't grow fast. The source of P is invariably fish food unless you have coral chips in the tank or are adding P to the tank as fertilizer.

I don't want to suggest you starve your Oto to death so I would rather suggest aggressive water changes to keep the P level down.

tt

[shihr]

the sun light may be affecting ur algae growth as well.. i had a tank by the window once.. and was full of algae..well until the tank started to settle in.. whats the logic behind that? high amonia nitrates and p that the (not yet established) beneficial bacteria cant cope yet? i was under the impression that beneficial bacteria only feed on ammonia and nitrites?

[Rattail]

The word "Cyano" has been used quite a bit above. There is a big difference between Cyano and algae. I suggest that you research to determine what it is that you have. If you are indeed feeding too much, it might very well be cyano. But first make sure.

As for not feeding your fish for a prolonged period - I would not. Rather feed VERY little.

[Rosemary]

@ Tyrone I'm feeding Dajanapet neon tetra micro granules to the CPD's which is what they were eating when I got them, and otto gets about 1/4 of a algae wafer tablet, about every second day.

@ Richard I have looked extensively at pictures and am fairly sure that it is cyano. It grows in 'webs' or mats over things, is fairly easy to pull off, has a musty smell to it, otto doesn't eat it, and because I have so few tiny fish in the tank, I've probably been over feeding.

The plan for now: I'll continue to feed otto his wafer bit, but stop feeding the CPD's for a few days while doing daily 50% water changes. Will keep you posted.

[tyronegenade]

Microgranulates tend to be very dense, nutrient wise. You need feed very little to the fish. It is very easy to overfeed. Try Rattail's advice and feed very little and see how things go.

What substrate do you have?

If you want to get control over nutrient levels I still have LOTS of Indian fern.

In the mean time I suggest you get 2 20L buckets. Fill one with water and let it stand overnight. Drain 50% of the water out with the other bucket and then add the fresh water from the 1st bucket. In a few hours time drain 75% of the water and replace with the fresh water. Then, every day for a week, do as big a water change as you can.

It could be that the problem is overfeeding.

What is you pH? Cyano bacteria do best at the alkaline end of the scale.

[Rosemary]

The substrate is pool filter sand.  pH on pH meter today 7.3, dipstick yesterday said just below 7. I have in the past added a bit of bicarb (about 1/6tsp) when starting the CO2 bottle, to buffer against pH drop if the CO2 went mad. But that was quite a few water changes ago.

WRT nutrient levels: I've got quite a few sunset hygro stems in there, and some other stems growing pretty fast. If I'm not winning in a few days I'll pm you. But, surely if I've done 7 sequential 50+% water changes, and a thorough vacuum with each, then there simply can't be much excess nutrient left? Where's the nutrient, if I've removed and replaced all the water? or is it in the substrate dirt?

CPD's down to rations of 2 granules each and counting...

[Rattail]

Ok, you say it IS cyano. Remember then that cyano is a bacteria and not an algae per sé and treatment should be approached accordingly.

If you had a bigger aquarium, I'd suggest using erythromycin, (go read what happened in this thread http://www.apsa.co.za/board/index.php?topic=342.0 ) but as your tank is very small, I'd rather not say more than to point out that it is in fact a bacteria.

Good luck.

[tyronegenade]

The substrate is pool filter sand.  pH on pH meter today 7.3, dipstick yesterday said just below 7. I have in the past added a bit of bicarb (about 1/6tsp) when starting the CO2 bottle, to buffer against pH drop if the CO2 went mad. But that was quite a few water changes ago.

Many algae, and Cyanobacteria, import bicarb (HCO3-) into their tissues using a symport system, that is they import the negatively charges bicarb together with a positive ion such as sodium. In adding NaHCO3 to your tank you are giving the cyno a distinct advantage over the plants. Don't use it.

If you aerate the water you will drive off excess CO2 and keep the pH above really critically low levels.

If you are going to add bicarb, use potassium bicarb (KHCO3) instead. Your plants will love it.

The silica sand will hold onto positively charged ions such as Ca and Mg which will attract phosphate etc... As such, the substrate becomes a store of these. Adding Na will displace Ca and Mg and thus also the phosphate. Keep doing the water changes and get rid of the Na part of the bicarb. Keep using Dirk's mix until the "algae" is under control. Dirk's hardening mix has lots of Ca and Mg in it which will precipitate the phosphate and keep it out of the water column. Keep doing the water changes in the mean time. Most cyanobacteria are not limited by nitrogen supply as they can fix atmospheric nitrogen.

If you pH drops below 6 don't worry too much... If it drops below 5 then you could be trouble.

If you want to keep your pH up try limestone chips instead. I have, accidentally, found this very effective. Sartijie (spelling?) should be able to help you out. My pH is hovering happily around 7 (bluddy irritating, I want it at 6!).

Added on...

At a pH of 7.3 about 94% of the C in the water is in the form of HCO3- and only 6% is CO2. This is making life difficult for your plants (which want CO2) and easy for the cynobacteria and real algae. You need to drop your pH down to 6 so at least 50% is CO2. Ditch the NaHCO3. If the pH drops below 6 then add a little bicarb, just enough to arrive at pH 6. Make it up in a water bottle (1 tsp/500 mL) and keep track of how many mL you need to add to get the proper pH. Remember, the pH will crash during the night and spike during the day so you have to set the pH at night.

bye