Green water again!

[Sue_Northumberland]

I'm sure this is the most asked about subject but I'm really struggling with cloudy green water in my small pond.

• Very small pond 18 months old, created in square shape with liner.
• Max dimensions 75cm wide x 150cm long x 40cm deep
• Hozelock Ecocel 5000 Filter & PondXpert MightyMite 3000 Pump Set
• Small solar powered bubbler
• Shade a.m. Sun p.m.
• Plants - Small water lily, hornweed, elodea densa, sagittarea graminea
• 3 gold fish, 1 largish, 2 small, fed small tsp of pellets daily if none remaining from previous day.
• Latest results from Tetra strip test: NO3 0, NO2 0, GH 8 deg, KH 5-6 deg, PH 7.2-7.6, CL 0?

Have tried lots of things over the 18 months with little success.
Most recently I was testing water once a week. If KH low, dosing with Tetra water stabiliser and then adding Algorem, cleaning sponge filter the following day with pond water and topping up with tap water treated with Tetra Aquasafe. This seemed to get water clear once a week but it was cloudy and green by following week. My water plants had started to thrive and I was hopeful I might reach some kind of balance soon.
However, after leaving pond in care of house sitters for 3 weeks, I return to stubbornly cloudy green water, almost no floating weeds and a feeling of despair! I know that pond weeds tend to sink in the winter, but I can’t find any by swishing around.
Is it too late in the year to add more?
Have my fish eaten the pond weed because I'm not feeding them enough?
Does the mosquito larvae covering the bottom of the pond cause algae?
Thanks for any encouragement/advice!

 

[JRS]

Welcome to the forum!

Looks like you have roughly 120 U.S. gallons. Something that makes me think you are feeding too much: pellets: "if none remaining from previous day". If you have any left over from the previous day it is definitely too much.

A pond with fish that still has mosquito larvae, not usual. Mosquito larvae float at the top typically along the edges, perhaps some other type of larvae or invertebrate feeding on organic matter or left over food? The larvae do not cause algae.

You are correct that a hungry goldfish will turn to plant matter, which includes many types of algae in the absence of concentrated food like pellets. Think salad vs steak. Many folks have had success by reducing or eliminating supplemental feeding and letting the goldfish graze on the algae in the pond.

The fish cannot eliminate green water which is caused by too many nutrients- the balance as you noted. Please consider a small bog filter next to your pond. The bog plants will consume the excess nutrients, eliminating the green water. I added a small one next to my pond and have not had a green water issue since. They require very little maintenance and do an excellent job for your ponds water quality, and the fish cannot not eat the plants like your floaters.

 

[addy1]

Welcome to the forum!

Good advice up there.
Small ponds are hard to balance.

 

[Mgessert]

I’m guessing your fish sitter over fed, leading to the algae buildup. I would definitely add plants back in, maybe some that sit with their roots in the water but the fish can’t get to. My fish chewed on my water lilys until I started feeding them leafy greens. If it’s only 100 gal then you might be maxed out with fish waste and feed. Try feeding what they’ll consume in just a few minutes. Can you post some photos? Also, if the temp is dropping, they’ll need less feed, until you will stop feeding when the water temp is below 60F.

 

[Sue_Northumberland]

Thanks for all your comments and suggestions, they are very helpful. I guessed at mosquito larvae because I don't really know what they are. In this post of the world we have a lot of midges. The larvae are tiny and sit in little tubes that decorate the liner in neat rows - I discovered then when I half emptied the pond in a previous attempt to deal with the green water. There are also creatures that build little tubes nests in the bottom from small gravel. I have taken a photo so that you can see how an adjacent bog garden unfortunately wouldn't work - the pond has built up sides. How do I attach a photo to this reply?

 

[Sue_Northumberland]

I see now how to attach a photo!

 

[YShahar]

It's really hard to create a working ecosystem in a small volume of water, so it's likely that you'll have periodic bouts of green water. One thing that you can do is build some kind of up-flow bog filter to starve out the algae. This wouldn't need to be very large; you could run your water through the bottom of a long planter and have it filter up through gravel of different sizes and it might be enough. Then you simply let the water flow back into the pond.

The key to getting clearer water is:

1. Slow-flowing water passing through lots of gravel. This provides surface area for beneficial bacteria to grow on. Their job is to convert the ammonia produced by the fish into nitrites and nitrates.
2. Lots of plants both in the pond and in the bog filter. Their job is to consume the nitrogen compounds.

But definitely don't feed the fish more than they can consume in about a minute! In fact, with insect larvae and algae in the pond you probably needn't feed them at all; they'll find plenty to eat on their own. What you can do is give the fish a couple of pellets each at a set time during the day, just to keep them socialized.

Think of the pellets as junk food, while the algae is the actual fish food. Basically you want to reduce the amount of organic matter in the water as much as possible. This included uneaten food (which begins to break down immediately) and fish poop.

Cheers!

 

[Sue_Northumberland]

Thanks for that YShahar. The fish don't come to feed on the pellets any more, which they did before we went on holiday, so even if I only put 6 pellets in those pellets don't get eaten in a minute. Usually they have gone by the next day and I assume the fish have eaten them at their leisure. I'll just stop feeding them altogether now. Do I ever have to worry about them starving? The algae is not in the form of strings, so I'm not sure how the fish will feed on the green water. I'll get some more plants, though I'm not sure how well they'll thrive now the water is getting colder.

 

[j.w]

@Sue_Northumberland

 

[YShahar]

Thanks for that YShahar. The fish don't come to feed on the pellets any more, which they did before we went on holiday, so even if I only put 6 pellets in those pellets don't get eaten in a minute. Usually they have gone by the next day and I assume the fish have eaten them at their leisure. I'll just stop feeding them altogether now. Do I ever have to worry about them starving? The algae is not in the form of strings, so I'm not sure how the fish will feed on the green water. I'll get some more plants, though I'm not sure how well they'll thrive now the water is getting colder.

Do you have blanket algae growing on the surfaces inside your pond? If so, then your fish will happily munch on that. If they aren't coming up and begging for food, they're probably finding enough to eat. You could try putting a couple of pellets in whenever you see them congregating and see if you can teach them to come up and eat a certain time.

I don't know the climate at all where you are, but probably folks on the forum who live near you (or in similar climates) can help in plant selection. Where I am (Israel) calla lilies will flourish all winter long, while water lilies go dormant, and water hyacinths die back altogether. So I'm putting in lots of calla lily bulbs in all the gravel pockets around the pond to boost filtration.

But even without plants, if you can run your water through lots of gravel, that will help in terms of filtration. Search the forum for "bog filter" and you'll find all sorts of variations on the theme, including some really clever planter-based "bogs". Also check out the videos of Ozponds in Australia, as he's got lots of information on building simple DIY filters for small ponds.