Correct about midge larva (I believe after more looking that those are Chironomidae). But no harm done if frog or toad. To NOT if they are salamanders and they probably would die.
Now, the timeline. These eggs are 'hatching'. They were probably laid about 20 or 21 Feb. This also fits with the fact that most salamanders are early breeders. And if these were frogs or toads you would have heard them in February.
Playing Sherlock Holmes a bit here😀
Bill
PS. A hydrogen peroxide bath and distilled water rinse is my normal for adding plants to an aquarium. Obviously I couldn't boil them if they were to grow. Clean hands and tools a must if working in an aquarium.
I eat the store bought greens raw, so hope they are already clean enough to feed other animals (like guests).
A final thought. Hay in water produces lots of tiny organisms. Food for the tadpoles. Use an eyedropper.

Some conjecture: The tadpole stage in salamanders have a distinctive difference.
Salamanders are primarily carnivorous, sight feeders as tadpoles. That is why f&t tadpoles have the eyes they have. They eat algae. It cannot escape. It is easy to find.In adults the eyes are more similar, both f&t and salamanders are predatory. They have binocular vision, yet see all around to avoid predators.
In f&t the stage is set, the eyes need little restructuring to adult. With salamanders it must be otherwise, eyes must reconfigure more. Again, conjecture. We will see as they mature.

Another point👍

Increase the odds on being a salamander. They are primarily predators on small arthropods. The mouth is wider, as seen, than the mostly algae grazing frog and toad tadpoles, which are 'beaked'. And toothed.

Notice the predator,s forward facing eyes. Frog and toad tadpoles are bulging from sides of the head, eye proper not seen in frontal view.

Aerate and keep with the snails. They may eat their eggs. They may eat brine shrimp, too, but they (the shrimp) will die quickly when put in fresh water. Cleanliness is essential. Bacteria 'bloom' suddenly and use the oxygen. Aeration and water changes a must. Methaline blue, I think it is called, for Ick in fish KILL most organisms NOT fish or plants. That is my experience. Once. Never tried that again.
Hope you get some to next stage. Thanks for YOUR efforts. In all this.
Bill

I actually thought napabob would be the first to give in to this temptation.
One of the funniest of all lines.
Bill

At the risk of wearing this subject thin.
There are seven introduced amphibians in England. This makes things a bit trickier.
The pet trade has spread many lower animals to foreign countries goldfish, carp, we now have English sparrows and starlings, gipsy moths and others. Our native bullfrog has spread to other countries and into areas in the US where it threatens native fauna. Pheasants, Chinese and European mantids and a few lady bugs have been a plus to our native Fauna, our Flora has suffered less well. Nature set this up, man meddles. To his ultimate detriment, in most cases.
I found a river frog, Lithobates heckscheri, (also called pond frog), in Cambridge, Maryland. Have photo documentation. They are not from here. No other record in MD that I can find. So you may have something new to you.( Where have I heard that before)?
OK. Off the soap box.
Bill

Another ID point for salamanders, the front legs bevelope first, where with frogs or toads, it is the rear.
What is the main source of these tadpoles? And a timeline, when you first saw them and at what stage of development? Put bits of leafy greens in the water. This will be nibbled, but you may need protein for final development.

Are you making a difference between newts and salamanders?
All newts are a suborder of salamanders, but all salamanders are not newts. There are seven amphibians in , or on, the island I think of as England. Three newts, two each toads and frogs. No toads or frogs native to said island have external gills in the tadpole stage. The three salamanders do. QED. The odds that the tadpoles shown by Brenda are newts , or salamanders.
My caveat is that I have been wrong before. I am anxious for any discussion on this.
Please have some documentation, as I like to peruse this type thing.

Forgot to mention. If you are interested, there is a free download.
A Guide to Larval Amphibian ID in Field and Laboratory.
Perdue U. Good general information.

Morning all.
After about an hour looking into this I find.
There are seven native English amphibians. Three newts, two each frogs and toads (accd. to Encyclopedia Brittania). While there are frog tadpoles that have external gills, none in England..
I have raised frog, toad and some salamanders to adult from eggs. In my opinion these are salamanders.
Frog and toad poles are oval and stocky. Gills are covered by an opercullum.
In salamanders body is squarish and tail is somewhat slimmer.
When these develop legs you will know. If these are salamanders they will have ' walking' legs.
Tadpoles sometimes gulp air, same as goldfish. They have both lungs and gills. Gills disappear in MOST adults and they then breath with lungs and thru their skin.
Salamander tadpoles tend to be carnivorous. They eat "mozzies" and copeopods and other creatures. Tiny insects like aphids may be eaten, not bits of meat as I have seen suggested. Fouls the water.
As they mature, provide a way to get out of water.
Enjoy this. Common but rarely seen, it is nature. Just think, only one or two of these will live to breed.
Then just turn them loose in your yard for a repeat performance next spring.
Bill

Mark got it, a salamander.

At the risk of befouling this thread, I feel that MAGA is oxymoronic under the current administration.
Bill

You took the easy one. Is the other a trip?.
Bill
By the way, the above oops is my tablet spell checker. It has yet to get entomolese. That is THRIP.
Bill

I forgot to mention. If they will not obey, try kindness. Flogging is cruel😀😀

I agree with Mark in setting up the shot in a controlled condition. For one thing you can put specimens in clean water. Then you can experiment with lighting to avoid glare. Lastly you can get set up, cool specimens and be ready as they emerge from torpor.
I wonder if these are toad tadpoles. Not knowing timeline, it is hard to say from your photos. This is the right time of year for salamander tadpoles, but early for toads. In the US, at least.
But if these are developing rapidly that says toad. Spadefoot toads can go from heavy rain, leaving large puddles, to baby toads in between two and three weeks. Toads in the family bufonidae not as fast.
If in a few days, if they still have gills, then salamanders. These eat some algae, but will need diatoms and other arthropods for food later to mature.

Don't you love microcosms, tho. Always something new.☺️